Bike Tire Pressure Calculator – Front and Rear PSI for Your Weight
The pressure printed on your sidewall is a maximum, not a recommendation. What your tires actually need depends on how much weight each wheel carries and how wide the tire is. Enter your rider, bike and gear weight, your tire width and the surface you ride, and this calculator works out front and rear pressures from Frank Berto’s classic 15% tire-drop research — the starting point behind most modern pressure guides.
You, the bike and the tire
Advanced options — surface, setup and maximum pressure
The advanced fields below are already included in the result with their default values — open Advanced options to change them.
🔒 Everything is calculated in your browser — nothing you enter leaves your device.
Your pressures
The working
How to use these numbers
Treat them as a well-founded starting point, not a command. Set both tires, ride your usual roads, and adjust by 2–3 psi at a time: down if the bike chatters and skips on rough surfaces, up if it feels wallowy in corners or you are bottoming out on bumps. Never exceed the lower of the maximums printed on your tire and your rim.
- Pressures come from Frank Berto’s classic 15% tire-drop research — the starting point behind most modern pressure guidance.
- The calculator starts from total system weight, never body weight alone, and splits it across the wheels — about 45% front and 55% rear in a road position.
- Wider tires need less pressure: the default 85 kg system on a 28 mm tire gives 61 psi front and 74 psi rear, and the width table shows why narrow tires at heavy loads hit their limits fast.
One rider, many widths
Same rider, same bike, same surface — only the tire width changes. This is why wide tires do not need high pressure, and why narrow tires at heavy loads run into their limits so fast.
| Tire width | Front | Rear |
|---|---|---|
| 23 mm | 86 psi | 103 psi |
| 25 mm | 74 psi | 90 psi |
| 28 mm | 61 psi | 74 psi |
| 32 mm | 49 psi | 59 psi |
| 35 mm | 42 psi | 51 psi |
| 40 mm | 33 psi | 40 psi |
| 45 mm | 27 psi | 33 psi |
| 50 mm | 23 psi | 28 psi |
| 55 mm | 19 psi | 23 psi |
| 60 mm | 17 psi | 20 psi |
The table follows your inputs live — change the weight or the surface and every row moves. Widths beyond the 37 mm edge of Berto’s original chart follow the same fitted curve, which is why very wide tires at light loads show pressures that call for a good gauge and a feel for the trail.
Why honest calculators disagree
There is no single true pressure hiding behind the math. Berto’s drop method, used here, answers “what pressure makes the tire deform by its ideal 15% under this load?” Newer impedance-based calculators answer a different question — “where does vibration start costing speed on this surface?” — and account for casing stiffness and measured (not labelled) width. On the same rider those models can land 5–10 psi apart, and both are defensible. Use this page’s numbers as your baseline, then let your roads and your hands settle the last few psi.
Pairs well with this calculation
The conversions you end up needing around any bike setup — weights, sizes and the volumes in your bottles and bags.
The right pressure in three steps
Weigh the whole system
Your tires do not know what is you and what is bicycle. Rider, bike, bottles, bags and kit all sit on the same two contact patches, so the calculator starts from the total and never from body weight alone.
Split the load
You do not sit in the middle of the bike. A road position puts roughly 45% of the load on the front wheel and 55% on the rear — measured figures Bicycle Quarterly published for real bikes — so the two tires need different pressures, the rear always higher.
Read the drop chart
Frank Berto measured the pressure that makes a loaded tire squat by 15% of its height — the drop where comfort, grip and rolling speed meet. The calculator reads his chart for your two wheel loads and width, then adjusts for surface and setup.
How the bike tire pressure calculator works
pressure = 572.1 × wheel load0.944 ÷ tire width1.703 × surface × setup
The example on this page. An 85 kg system in a road position puts 38.3 kg on the front wheel and 46.8 kg on the rear. On a 28 mm tire the formula gives 61 psi front and 74 psi rear — 4.21 and 5.10 bar. Change nothing but the width, to 45 mm, and the same rider needs only 27 front and 33 rear.
Where the formula comes from. It is a power-law fit to the 15%-drop chart Frank Berto published (“Under Pressure”, 2004) and Bicycle Quarterly reprinted, with wheel load in kilograms and width in millimetres. Against the chart’s own worked example — 45 and 55 kg wheel loads on 20 mm and 37 mm tires — the fit lands within 1.3% on all four points: 125, 155, 45 and 53 psi.
The adjustments. Berto’s article advises lowering pressure on rough and unpaved roads and raising it slightly on very smooth ones; the surface menu applies +5% for smooth pavement, −8% for rough chip-seal and −15% for gravel. Tubeless setups, freed from pinch flats, conventionally run a little lower still, so the tubeless option applies −7%. These are stated, deliberate adjustments — not hidden fudge — and the working panel shows every multiplier that touched your numbers.
How the numbers are rounded. Pressures are calculated at full precision and rounded to whole psi only for display, since that is what a pump gauge can honestly show. Bar is converted from the displayed psi (1 psi = 0.0689476 bar) and shown to two decimals.
Going deeper
Stand a loaded bike on flat ground and the tire squashes where it meets the road. Tire drop is how much the axle sinks compared with the unloaded tire — expressed as a share of the tire’s height. Too little pressure and the drop is large: the casing flexes excessively, rolling resistance climbs, and a sharp bump can slam the rim into the ground through the tire, the classic pinch flat. Too much pressure and the drop shrinks toward zero: the tire stops absorbing the road and starts bouncing off it, which costs comfort, grip and — on real, imperfect surfaces — speed.
Berto, an engineer who worked with tire companies including Michelin and Continental, measured drop across tire widths and loads and found the balance point near 15%: enough flex to absorb the road, not so much that the casing wastes energy. Jan Heine’s later rolling-resistance tests for Bicycle Quarterly found the same neighbourhood from the other direction — beyond the pressure that produces roughly 15% drop, extra air bought no measurable speed. That is the chart this calculator is fitted to.
Three honest limits. First, Berto measured 700C tires up to 37 mm wide; this calculator extends the same fitted curve to 70 mm, and while it tracks modern wide-tire experience reasonably, pressures at the extremes are extrapolations, not measurements. Second, the model knows nothing about your casing: a supple race casing and a stiff puncture-armoured one behave differently at the same pressure, and labelled widths are not measured widths — a “28” that measures 30 needs the 30 row. Third, rim width matters: a tire far wider than its rim can feel unstable at low pressure no matter what any chart says.
And one rule that outranks every number on this page: never inflate past the lower of the maximum pressures printed on your tire and your rim. Hookless rims in particular carry lower limits than the tires mounted on them. If the calculator’s answer passes your limit, the limit wins — and the real fix is a wider tire, which is exactly what the width table above shows.
Five variations that teach the model
The default rider — 75 kg of rider, 9 kg of bike and 1 kg of gear, an 85.0 kg system on 28 mm tires, road position, average road, inner tubes — runs at 61 psi front and 74 psi rear (4.21 bar front, 5.10 bar rear). Every figure in this section was produced by changing the stated control on this page and reading the result back. Each variation changes one input only, so each difference is that input’s own effect, isolated.
Wider tires, much less pressure. Moving from 28 mm to 45 mm tires, with the same rider and the same road, drops the pressures from 61/74 psi to 27/33 psi — less than half, for the same weight. The page’s own width table shows why this is a curve and not a step: 23 mm needs 86/103 psi, 25 mm needs 74/90, 28 mm needs 61/74, 32 mm needs 49/59, 35 mm needs 42/51, 40 mm needs 33/40, 45 mm needs 27/33, 50 mm needs 23/28, 55 mm needs 19/23 and 60 mm needs 17/20. Each millimetre of width buys less pressure than the last at the wide end, because the fitted curve divides by width raised to the power 1.703 — the rear working on the default is 572.1 × 46.8^0.944 ÷ 28^1.703 ≈ 74 psi, and width sits in the denominator with a large exponent. The practical rule is simple: if you go wider, drop the pressure a lot, not a little, or you will ride a wide tire at narrow-tire pressures and get the worst of both.
A heavier rider, higher everywhere. Raising the rider from 75 kg to 100 kg — a 110.0 kg system on the same 28 mm tires — lifts the pressures from 61/74 psi to 78/94 psi, or 5.38 bar front and 6.48 bar rear. That is a 17 psi rise at the front and 20 psi at the rear for 25 kg of extra system weight, and it shows why body weight alone is the wrong input: the tires carry rider, bike, bottles, bags and kit together, so a light rider on a heavy touring bike can need more pressure than a heavier rider on a light road bike. The split also widens with weight — the front-rear gap grows from 13 psi to 16 psi — because the rear wheel’s 55% share of a bigger total grows faster in absolute terms than the front’s 45% share.
Rough surfaces want less air. Switching the surface from average road to gravel and unpaved, at the same weight and width, drops the pressures from 61/74 psi to 52/63 psi — the 0.85 surface adjustment applied to both wheels. That direction surprises riders who assume rough ground needs harder tires, but the logic is the drop model itself: on rough surfaces a slightly softer tire deforms around obstacles instead of bouncing over them, keeping the contact patch on the ground. The calculator’s surface ladder runs from 1.05 on smooth new pavement down through 1.00 on average road and 0.92 on rough chip-seal to 0.85 on gravel, and each step is a judgement about the surface, not a measurement — which is why the page tells you to fine-tune by 2–3 psi at a time on your own roads after setting the calculated figure.
Tubeless buys a small, real discount. Switching from inner tubes to tubeless, at the same weight, width and surface, drops the pressures from 61/74 psi to 57/69 psi — the 0.93 setup adjustment, worth 4 psi at the front and 5 at the rear. The reason is not mysterious: without a tube to pinch, a tubeless tire can run softer before pinch flats become a risk, and the sealant handles the small punctures that would end a tubed ride. The discount is deliberately modest — tubeless does not license running a road tire at gravel pressures — and it stacks with the surface adjustment rather than replacing it: a tubeless gravel setup at 45 mm would combine the width, surface and setup effects, which is why the page’s preset for a gravel 45 mm tubeless build exists as a single click rather than three separate guesses.
Position moves the split, not the total. Switching from road position (45% front, 55% rear) to upright and city position (35% front, 65% rear), at the same 85 kg system, moves the pressures from 61/74 psi to 48/87 psi: the front falls 13 psi while the rear rises 13 psi, and the total load is unchanged. That is the clearest demonstration on the page that front and rear are separate problems: the same rider, the same bike, the same tires, but a different posture redistributes the weight and therefore the pressures. A rider who sets both tires equal, or who copies a friend’s pressures without copying the friend’s position, is ignoring the one input that decides the split. The racing position at 40/60 sits between the two, and the three positions together are measured figures published for real bikes, not guesses.
The variation table, at a glance
Each row starts from the default (85.0 kg system, 28 mm, road position, average road, inner tubes: 61/74 psi) and changes only what the row says.
| Variation (change from default) | Front | Rear | Change |
|---|---|---|---|
| Default | 61 psi | 74 psi | — |
| Tire width 45 mm | 27 psi | 33 psi | −34 / −41 psi |
| Rider 100 kg (110.0 kg system) | 78 psi | 94 psi | +17 / +20 psi |
| Surface gravel / unpaved (× 0.85) | 52 psi | 63 psi | −9 / −11 psi |
| Setup tubeless (× 0.93) | 57 psi | 69 psi | −4 / −5 psi |
| Position upright / city (35% / 65%) | 48 psi | 87 psi | −13 / +13 psi |
The table ranks the levers by size: width first by a wide margin, then weight, then position’s redistribution, then surface, then setup. A rider chasing comfort should therefore start with width, not with letting a few psi out of a narrow tire — and a rider chasing speed should remember that the pressure that feels fast on smooth pavement is the wrong pressure on gravel, by 9 to 11 psi on this page’s own adjustment. Change the big lever first; fine-tune with the small ones.
Using the numbers on the road
Start here, then tune by feel. The page’s own advice is the right method and bears repeating: treat the calculated pressures as a well-founded starting point, not a command. Set both tires, ride your usual roads, and adjust by 2–3 psi at a time — down if the bike chatters and skips on rough surfaces, up if it feels wallowy in corners or you are bottoming out on bumps. The calculated figure is the centre of a range, not a point: Berto’s 15% drop is a measured ideal for a loaded tire’s squat, and real tires, real rims and real roads all move the ideal by a few psi. A rider who treats 61/74 as a law will ride a worse bike than a rider who treats it as a starting point and listens to the road for a week.
Never exceed the lower maximum. The page offers an optional maximum-pressure field for exactly one reason: if the answer ever passes that number, the calculator warns you instead of quietly sending you out over the limit. The limit that binds is the lower of the maximums printed on your tire and your rim — a tire rated to 100 psi on a rim rated to 70 psi is a 70 psi system, and the heavy-rider variation above (78/94 psi on 28 mm tires) is exactly the case where a narrow tire’s or a rim’s limit can arrive before the calculated figure does. The pressure printed on the sidewall is a maximum, not a recommendation, and the gap between the two is the whole point of this calculator: the sidewall tells you what the tire survives, the calculator tells you what the load needs, and the smaller of the two governs.
Why honest calculators disagree. There is no single true pressure hiding behind the maths, and the page is unusually frank about it. Berto’s drop method, used here, answers the question “what pressure makes the tire deform by its ideal 15% under this load?” Newer impedance-based calculators answer a different question — “where does vibration start costing speed on this surface?” — and account for casing stiffness and measured rather than labelled width. On the same rider those models can land 5–10 psi apart, and both are defensible, because they optimise different things. Use this page’s numbers as your baseline, then let your roads and your hands settle the last few psi — and do not treat a disagreement between two good calculators as evidence that one of them is broken.
The wide-tire caveat, stated plainly. Widths beyond the 37 mm edge of Berto’s original chart follow the same fitted curve, which is why very wide tires at light loads show pressures that call for a good gauge and a feel for the trail — the 60 mm row of the width table reads 17/20 psi, figures that demand an accurate gauge and a sense of what the tire is doing underneath you. The fitted curve is an extrapolation past 37 mm, not a measurement, and extrapolations deserve more scepticism than interpolations. If you ride very wide tires, treat the table’s wide rows as a starting point in the same spirit as the rest of the page, and pay more attention to the 2–3 psi tuning process than to the printed row. The model is honest about its edge; the rider should be honest about it too.
Units, without the usual confusion. The calculator works in kilograms and millimetres by default, with a pounds option for the weights, and reports pressures in both psi and bar — the default 61/74 psi reads as 4.21 bar front and 5.10 bar rear. Tire width is the number after the × on the sidewall, so 700×28 means 28 mm, and the page covers 23–70 mm. The conversions matter because the two most common pressure errors are unit errors: a rider who enters pounds as kilograms, or who reads a bar figure as psi, will be wrong by far more than any model disagreement. If your gauge reads bar and your friends talk psi, use the page’s paired figures rather than converting in your head on the roadside.
Gravel pressures: between road and trail
Gravel riding sits between mountain biking and road riding, and its pressures sit between them too. A gravel tire, 35 to 45 mm wide, tubeless, on a drop-bar bike, runs at higher pressures than a mountain bike tire, because the tire is narrower, the volume is smaller, and the surfaces are smoother, but at lower pressures than a road tire, because the surfaces are looser and rougher than pavement. The published starting points for gravel, tubeless, are 38 to 42 psi for a 35 mm tire, 34 to 38 psi for a 40 mm tire, and 30 to 34 psi for a 45 mm tire, for a rider in the middle of the weight range, with the same weight and terrain adjustments as the mountain bike tables: heavier riders higher, looser surfaces lower, smoother surfaces higher. The calculator on this page computes a starting point from the system weight, the tire width, and the front and rear split, and the gravel ranges are the starting points for the same test method: start in the range, adjust by feel in 1 psi steps, and stop 1 psi above the floor where rim strikes or squirm begin.
The gravel rider’s pressure decision follows the same steps as the mountain biker’s: width, weight, terrain, tubeless setup, and the safety rule. The terrain adjustments are smaller, because gravel surfaces vary less than trails, but they are not absent: a ride that includes singletrack, mud, or rough fire road rewards the lower end of the range, and a ride that is smooth hardpack rewards the higher end. The casing matters as for any tire, and an insert, where used, permits the same 3 to 5 psi reduction. The companion guide on mountain bike pressures explains the test method and the terrain adjustments in full, and the companion guide on road pressures explains the 15 percent tire-drop model this calculator implements. The safety rule governs gravel as it governs every tire: never exceed the lower of the tire and rim maxima, printed on the sidewall and stated by the rim maker.
Units and gauges: psi, bar, and the cold check
Tire pressure is stated in psi in the United States and in the United Kingdom’s cycling culture, and in bar in much of Europe, and the two units describe the same pressure: 1 bar is about 14.5 psi, so the calculator page’s worked example of 61 psi front and 74 psi rear is about 4.2 bar front and 5.1 bar rear. The conversion matters because pumps, gauges, and tire sidewalls use both units, and a rider who reads a bar gauge against a psi target, or the reverse, will inflate the tire far from the intended pressure. The page’s paired figures, showing both units where the context needs them, are the safe reference, and a conversion done in the head, on the roadside, is a conversion likely to be wrong. Use the page’s figures, or a gauge that reads in the unit the target is stated in, and check the unit before the pressure.
The gauge matters as much as the unit. Gauges differ by several psi, and the rider’s adjustments, 1 or 2 psi for terrain, for the wet, or for feel, are meaningful only against a consistent gauge. The same gauge should be used for every measurement, the pressure should be measured cold, before the ride, because riding warms the air in the tire and raises the pressure by 1 or 2 psi, and the pump’s gauge should be checked against a known-accurate gauge periodically. A tire checked warm and deflated to the target pressure is under-inflated for the cold start, and a tire inflated in a warm garage and ridden in cold air reads lower on the road, by about 1 psi for every 10 degrees Fahrenheit of temperature change, approximately. The habit is simple: check cold, with the same gauge, before the ride, inflate to the calculated figure, adjusted for the surface, and ride. The record, noting the tire, the width, the weight, the pressure, and the feel, turns the starting point into the rider’s own working pressure, ride by ride.
Frequently asked questions
What tire pressure should I run?
The pressure that supports your actual wheel loads at about 15% tire drop for your tire width — which is what this calculator works out. As an example, an 85 kg rider-and-bike system on 28 mm tires, split 45/55 across the wheels, comes out at 61 psi front and 74 psi rear on an average road. Heavier riders and narrower tires push the numbers up; wider tires bring them down fast. Start from the calculated figure and fine-tune by feel, a few psi at a time.
Why are the front and rear pressures different?
Because the wheels carry different loads. In a normal road riding position about 45% of the total weight rests on the front wheel and 55% on the rear — figures Bicycle Quarterly measured on real bicycles, with racing positions nearer 40/60 and upright city bikes nearer 35/65. A tire’s needed pressure follows its load, so the rear tire, carrying roughly a fifth more weight, needs roughly a fifth more pressure. Running both tires at one pressure overinflates the front or underinflates the rear.
Should I just use the pressure printed on the sidewall?
No. The number on the sidewall is a maximum the tire must not exceed (some tires also print a minimum), not a recommendation for you. It is set for the heaviest load the tire might ever carry, which is why inflating to it usually overinflates wide tires and, per Berto’s chart, can still underinflate narrow ones under heavy riders. Use it as the ceiling it is: your pressure should come from your weight and width, and it must never pass the lower of the tire’s and rim’s maximums.
Why does this calculator give different numbers from Silca or a brand calculator?
Because the models ask different questions. This page is built on Berto’s 15% tire-drop method: the pressure at which the loaded tire deforms by its ideal share. Silca’s and several brands’ calculators are built on impedance research — the point where vibration losses on a given surface start costing speed — and factor in casing type and measured width. On the same rider the two families of models can differ by 5–10 psi and both are published, defensible methods. Treat any calculator’s output as a starting point and settle the final few psi by riding.
Does tubeless really let me run lower pressure?
Yes, within reason. The traditional floor on pressure is the pinch flat: a bump drives the rim into the tube. Tubeless setups have no tube to pinch and sealant closes small punctures, so riders conventionally run somewhat lower — this calculator applies a 7% reduction for the tubeless option. Lower is not free, though: go too far and the tire can squirm in corners or burp air off the rim on a hard hit, and your rim’s own maximum and minimum guidance still applies.
How do I convert between psi and bar?
Multiply psi by 0.0689476 to get bar, or divide bar by the same number to get back. The pressures on this page are shown in both: the default example of 61 psi front and 74 psi rear is 4.21 and 5.10 bar. Most floor pumps carry both scales on the gauge; track pumps aimed at mountain bikes often read low enough to make the small numbers on wide tires easy to set accurately.
Why is the rear tire always higher?
Because the rear wheel carries more of you. In the road position the load splits 45% front and 55% rear — 38.3 kg front and 46.8 kg rear on the default 85.0 kg system — so the rear tire needs more pressure to reach the same 15% drop, giving 61 psi front and 74 psi rear. The split is a property of your position, not of the tires: switch to the upright position at 35% front and 65% rear and the same system needs 48 psi front and 87 psi rear. Equal pressures front and rear would mean the front is over-inflated and the rear under-inflated at the same time.
Should I just use the pressure printed on the sidewall?
No — the sidewall figure is a maximum, not a recommendation. What your tires actually need depends on how much weight each wheel carries and how wide the tire is, which is why the default rider on 28 mm tires needs 61/74 psi even though the tire may be rated far higher. Never exceed the lower of the maximums printed on your tire and your rim, and use the optional maximum-pressure field on this page: if the calculated answer ever passes it, the calculator warns you instead of quietly sending you out over the limit.
How much does going tubeless change?
On this page, 4 psi at the front and 5 at the rear: the default 61/74 psi becomes 57/69 psi with the 0.93 tubeless adjustment, everything else unchanged. Without a tube to pinch, a tubeless tire can run softer before pinch flats become a risk, and sealant handles the small punctures that would end a tubed ride. The discount is deliberately modest — tubeless does not license running a road tire at gravel pressures — and it stacks with the surface adjustment rather than replacing it.
Why do wider tires need less pressure?
Because a wider tire spreads the same load over a larger contact patch, so less pressure achieves the same 15% drop. The page’s own width table makes the curve visible: the default rider needs 86/103 psi on 23 mm tires, 61/74 on 28 mm, 33/40 on 40 mm and just 27/33 on 45 mm. The fitted curve divides by width raised to the power 1.703, which is why each extra millimetre buys less pressure saving at the wide end — and why going wider without dropping the pressure leaves you riding a wide tire at narrow-tire pressures, getting the worst of both.
What pressure should gravel bike tires be?
Published tubeless starting points are 38 to 42 psi for 35 mm, 34 to 38 psi for 40 mm, and 30 to 34 psi for 45 mm tires, adjusted for rider weight and terrain as for mountain bike tires, and tested by the same method: start in the range, adjust in 1 psi steps, and stop 1 psi above the floor where rim strikes or squirm begin.
Does temperature affect bike tire pressure?
Yes, by about 1 psi per 10 degrees Fahrenheit, approximately. Inflate and check tires cold, before the ride, with the same gauge, and allow for the change between the inflation temperature and the riding temperature. A tire checked warm reads 1 to 2 psi higher than the same tire cold.
Do tubeless tires need less pressure than tubed tires?
Yes, roughly 3 to 5 psi less than the same tire with a tube, because there is no tube to pinch. The tubeless floor is set by rim strikes and by burps, the bead seal breaking under lateral load, rather than by pinch flats. An insert permits a further 3 to 5 psi reduction.
Related calculators
Weights, sizes and measures — the rest of the shelf.
Kg to Lbs Converter
Weights in the other unit, both ways.
Mm to Inches Converter
With the fractions a ruler can read.
Litres to Gallons Converter
US and Imperial, side by side.
Celsius to Fahrenheit Converter
For the mornings you decide by temperature.
Conversion Calculator
Everyday units, all in one place.
What PSI Should Mountain Bike Tires Be? Pressure by Terrain and Tubeless Setup
Mountain bike tire pressure is a starting point, not a number: it depends on the tire width, the rider’s weig…
Road Bike Tire Pressure: How to Calculate It and What Is Correct
Road bike tire pressure is calculated, not guessed: the Berto 15 percent tire-drop model gives a pressure for…