Wind Chill Calculator – What It Really Feels Like Outside
Enter the air temperature and wind speed — the temperature your skin actually feels.
The weather
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Advanced options — unit select, wind in every unit, Environment Canada category
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Converted from the wind speed above: 1 mph = 1.609344 km/h = 0.44704 m/s = 0.868976 knots.
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Environment Canada’s six risk bands, from the wind chill value above. The United States thresholds are in the frostbite table below.
The conversions and the Environment Canada category below are already worked out from the temperature and wind above — open Advanced options to see them, and use the unit select to switch the whole calculator between Fahrenheit/mph and Celsius/km/h.
Unit select, wind in every unit, Environment Canada category are already included in the result with their default values — open Advanced options to change them.
What it feels like
The numbers behind it
Frostbite check: no timed risk
The National Weather Service frostbite zones begin at a wind chill of -18°F (-28°C) or colder, where exposed skin can freeze in about 30 minutes. At 6°F the risk is slower — steady heat loss, numb fingers and discomfort — rather than a countdown. Dress for the wind chill, not for the thermometer.
The thermometer only tells half the story. Enter the air temperature and the wind speed and this calculator gives you the wind chill — the temperature your skin actually feels — using the official National Weather Service formula, together with the frostbite clock that comes with it. Warmer than the formula allows, or dead calm? It says so honestly and shows the real temperature instead of inventing a number.
Key takeaways
- Wind chill is the temperature exposed skin feels when wind strips away the warm layer next to it, worked out here with the official 2001 National Weather Service formula.
- Frostbite risk is set by the wind chill value: within 30 minutes at −18°F, within 10 minutes at −32°F, and within 5 minutes at −48°F.
- Wind chill applies to people, not thermometers: it never cools an object below the actual air temperature.
Contents
- See where it lands
- Pairs well with this calculation
- Wind chill in three steps
- How the wind chill calculator works
- Going deeper
- Wind chill chart: temperature against wind speed
- Environment Canada categories: the same cold, read the Canadian way
- Wind speed in mph, km/h, m/s and knots
- The formula, worked through, and where it stops applying
- Frequently asked questions
See where it lands
One scale, from deep-freeze cold on the left to the top of the wind chill range on the right. The shaded bands at the cold end are the National Weather Service frostbite zones; the two markers are your air temperature and the temperature your skin feels.
Wind chill 6°F — clear of the frostbite bands, which begin at -18°F.
Why the markers bunch up in strong wind
Wind chill grows with the 0.16 power of the wind speed, not in a straight line. The first 15 mph of wind does most of the damage; going from 30 to 60 mph adds far less than going from calm to 30. That is why the wind chill marker races left at low wind speeds and then crawls — and why a gale, miserable as it is, does not feel twelve times worse than a breeze.
Pairs well with this calculation
The rest of the weather shelf — what the air holds, and what the day will do with it.
Wind chill in three steps
Enter the air temperature
The plain thermometer reading, from a forecast or the gauge outside. Pick your units first if you think in Celsius and kilometres per hour — the Canadian formula is built in too.
Add the wind speed
Use the sustained wind from your forecast, not a passing gust. The formula raises it to the 0.16 power, adds and subtracts the temperature terms, and produces the feels-like temperature for exposed skin.
Read the frostbite clock
Below a wind chill of -18°F (-28°C), exposed skin is on a countdown: roughly 30 minutes, then 10, then 5 as it gets colder. The check under your result tells you which line you are past — or that you are clear of all three.
How the wind chill calculator works
Wind chill (°F) = 35.74 + 0.6215T − 35.75V0.16 + 0.4275TV0.16
T is the air temperature in °F and V the wind speed in mph. In metric the Environment Canada form of the same model is used: 13.12 + 0.6215T − 11.37V0.16 + 0.3965TV0.16, with T in °C and V in km/h.
The example on this page. Air 20°F, wind 15 mph. First the wind term: 150.16 = 1.542. Then 35.74 + 0.6215 × 20 = 48.17; 35.75 × 1.542 = 55.14; and 0.4275 × 20 × 1.542 = 13.19. Put together: 48.17 − 55.14 + 13.19 = 6.22, which rounds to a wind chill of 6°F — the day feels 14 degrees colder than it is.
When the temperature drops out. At 0°F with a 25 mph wind, both terms containing T vanish, leaving 35.74 − 35.75 × 250.16 = 35.74 − 59.83 = -24.09, a wind chill of -24°F. That is already inside the first frostbite band: exposed skin can freeze in about 30 minutes.
The same weather, Canadian style. Air -10°C, wind 20 km/h. The wind term: 200.16 = 1.615. Then 13.12 − 6.22 − 18.36 − 6.40 = -17.86, a wind chill of -18°C. The two formulas are one model fitted in two unit systems, and on the same weather they agree to within about a degree.
Why more wind stops helping. Hold the temperature at 0°F and raise the wind: 5 mph gives -11°F, 25 mph gives -24°F, 60 mph gives -33°F. The first 20 mph of wind costs 13 degrees; the next 35 mph costs only 9 more. The 0.16 power bends the curve flat, which the scale above shows as the marker slowing down as it moves left.
How the numbers are rounded. Results are rounded to the nearest whole degree, the National Weather Service convention — its published chart is all whole degrees, and this page’s values match that chart. The unrounded figure is shown in the results panel, so nothing is hidden by the rounding.
Going deeper
The National Weather Service draws three lines across its wind chill chart, and the frostbite check on this page is built on them. At a wind chill of -18°F (-28°C) or colder, exposed skin can develop frostbite in about 30 minutes. At -32°F (-36°C) or colder, the time falls to about 10 minutes. At -48°F (-44°C) or colder, about 5 minutes. They are guidelines, not guarantees: circulation, wet skin, alcohol and plain tiredness all shorten the clock, and children and older adults freeze faster than the average adult the chart assumes.
Environment and Climate Change Canada publishes its own risk categories in Celsius, with boundaries drawn at slightly different places, which is why Canadian guidance sometimes quotes different times for the same weather. This page uses the NWS lines in both unit modes — converted, never silently swapped — so a result means the same thing on both sides of the border. One distinction worth keeping: frostbite is about skin, and the wind chill index describes it well. Hypothermia, the fall of core body temperature, is a different danger driven by hours of exposure and inadequate clothing, and it can happen at temperatures well above the frostbite lines.
The current formula dates from 2001, when the National Weather Service and Environment Canada replaced the older index — built on how fast water cooled in Antarctic experiments in the 1940s — with a model based on human trials and the physics of heat loss from skin. It is defined only for temperatures at or below 50°F (10°C) and wind speeds of at least 3 mph (4.8 km/h). Warmer than that, moving air stops cooling you below the air temperature in the way the model describes; calmer than that, there is no measurable chill to add. That is why this page shows the plain temperature outside the range instead of stretching the formula where it does not belong.
Two assumptions ride along quietly. Forecast winds are measured 10 metres (33 feet) up, and the formula already adjusts them down to face level, so you can enter the forecast figure directly. And the model describes bare skin, in shade, at a walking pace. Sunshine can claw back several degrees of felt cold, clothing moves the lines a long way, and wet skin loses heat far faster. Read the number as exposed-skin truth, not as a verdict on your whole, dressed, moving self.
Wind chill chart: temperature against wind speed
Every cell in this table was produced by running this page’s own calculator, so the chart and the tool above cannot disagree. Read a row from left to right to see the wind’s bite grow, and read a column from top to bottom to see how the same wind matters far more on a bitter day than on a merely cold one. At 20°F a 40 mph wind takes the feels-like temperature to −1°F; at −20°F the same wind takes it to −57°F, where exposed skin can freeze in under two minutes.
| Air temperature | 5 mph | 10 mph | 15 mph | 20 mph | 30 mph | 40 mph |
|---|---|---|---|---|---|---|
| 20°F | 13°F | 9°F | 6°F | 4°F | 1°F | −1°F |
| 10°F | 1°F | −4°F | −7°F | −9°F | −12°F | −15°F |
| 0°F | −11°F | −16°F | −19°F | −22°F | −26°F | −29°F |
| −10°F | −22°F | −28°F | −32°F | −35°F | −39°F | −43°F |
| −20°F | −34°F | −41°F | −45°F | −48°F | −53°F | −57°F |
The frostbite clock that belongs with this chart is published by the National Weather Service in three thresholds: exposed skin can sustain frostbite within 30 minutes when the wind chill is −18°F or colder, within 10 minutes when it is −32°F or colder, and within 5 minutes when it is −48°F or colder. Those thresholds are the coarse version of the story. The full NWS chart shades frostbite time by the combination of temperature and wind, so two afternoons can share a wind chill yet sit in different shaded bands: the chart’s shading is the finer truth, and the three thresholds are the safe summary. The calculator’s own bands use the same −18°F, −32°F and −48°F cut points, which is why its verdict line and this table agree.
One more limit belongs here. Wind chill is defined for a walking adult’s exposed face at roughly head height, in the wind reported at the standard anemometer height. Sheltered spots, a car interior, or a windbreak change the real wind on your skin, and children, older adults, and anyone wet or tired lose heat faster than the model assumes. Treat every frostbite time as an outside limit for a healthy adult, not a guarantee for anyone.
Environment Canada categories: the same cold, read the Canadian way
Canada uses the same 2001 wind chill formula as the United States, but it publishes the risk in six bands rather than three thresholds, and the Advanced options panel above shows which band your wind chill falls into. The bands are Environment Canada’s, reproduced from its wind chill index guidance, and they are worth knowing because Canadian forecasts quote them directly: a forecast wind chill of −35 in Winnipeg is not just a number, it is a High risk band with a 10-to-30-minute frostbite clock attached.
| Wind chill (°C) | Risk | What it means |
|---|---|---|
| 0 to −9 | Low | Slight increase in discomfort; dress warmly |
| −10 to −27 | Moderate | Uncomfortable; risk of hypothermia and frostbite if outside for long periods without protection |
| −28 to −39 | High | Exposed skin can freeze in 10 to 30 minutes; check face and extremities for numbness or whiteness |
| −40 to −47 | Very high | Exposed skin can freeze in 5 to 10 minutes; very high risk of frostbite |
| −48 to −54 | Severe | Exposed skin can freeze in 2 to 5 minutes; severe risk of hypothermia on long exposure |
| −55 or colder | Extreme | Exposed skin can freeze in under 2 minutes; outdoor conditions are hazardous |
The two systems never contradict each other; they slice the same scale differently. The United States 30-minute threshold (−18°F, about −28°C) sits at the top of Canada’s High band, the 10-minute threshold (−32°F, about −36°C) sits inside it, and the 5-minute threshold (−48°F, about −44°C) sits inside Canada’s Very high band. The small differences come from rounding between Fahrenheit and Celsius and from the chart shading, not from different physics. One genuinely different thing is warnings: Environment Canada issues extreme cold warnings at thresholds that vary by region, because a wind chill that is dangerous in southern Ontario can be an ordinary winter day on the Prairies, so a warning in one city is not comparable to a warning in another.
For the calculator’s default afternoon, 20°F at 15 mph, the wind chill is 6°F, which is about −14°C, in Canada’s Moderate band. That matches the verdict above: no timed frostbite risk, but genuine discomfort on long exposure without protection. For a bitter case, −10°F at 30 mph, the wind chill is −39°F, about −39°C, at the cold edge of High and one degree from Very high: the clock is 10 to 30 minutes, and covering every patch of skin is no longer optional.
Wind speed in mph, km/h, m/s and knots
The calculator’s two systems pair temperature with wind speed: Fahrenheit with miles per hour, Celsius with kilometres per hour. That pairing is convenient, but real forecasts mix units freely: aviation and sailing use knots, science uses metres per second, and road and trail forecasts use kilometres or miles per hour. The Advanced options panel converts your wind speed into all four at once; the table below gives the same conversions for round numbers so you can read a foreign forecast without a calculator.
| mph | km/h | m/s | knots |
|---|---|---|---|
| 5 | 8.0 | 2.2 | 4.3 |
| 10 | 16.1 | 4.5 | 8.7 |
| 15 | 24.1 | 6.7 | 13.0 |
| 20 | 32.2 | 8.9 | 17.4 |
| 30 | 48.3 | 13.4 | 26.1 |
| 40 | 64.4 | 17.9 | 34.8 |
| 60 | 96.6 | 26.8 | 52.1 |
The exact factors are 1 mph = 1.609344 km/h, 1 mph = 0.44704 m/s, and 1 mph = 0.868976 knots; a knot is one nautical mile per hour, and a nautical mile is defined as exactly 1,852 metres. Converting is only half the job, though, because the wind chill formula itself takes miles per hour: if your forecast gives 24 km/h, that is 15 mph, and the wind chill at 20°F is 6°F. Entering the kilometre figure into a miles-per-hour field would give a colder, wrong answer, which is why the unit select in Advanced options switches the whole calculator, not just the label.
Clothing is the other half of the story, and it is where the model’s limits show. Wind chill describes exposed skin; a windproof outer layer restores the warm layer the wind would otherwise strip away, which is why a calm, windproof jacket changes the experience more than a thicker sweater under a porous coat. Cover the face, ears and hands first, because those are the parts that freeze first, and keep the skin dry: wet skin loses heat far faster than dry skin, so sweat-soaked gloves or a wet scarf undo the protection they appear to give. Layers work because they trap still air; the windproof shell exists to keep that air still.
The formula, worked through, and where it stops applying
The wind chill formula in Fahrenheit and miles per hour is: wind chill = 35.74 + 0.6215 × T − 35.75 × V^0.16 + 0.4275 × T × V^0.16, where T is the air temperature in degrees Fahrenheit and V is the wind speed in miles per hour. It was developed in 2001 from experiments on volunteers in a wind tunnel, replacing an older formula that overstated the cold, and it is the formula both the National Weather Service and Environment Canada use. The 0.16 power is the signature of the model: wind matters most at low speeds and then saturates, which is why the chart rows flatten as the wind rises.
Worked through for the calculator’s default, 20°F at 15 mph: first, 15^0.16 is about 1.5424. Then 35.74 + 0.6215 × 20 gives 48.17; subtract 35.75 × 1.5424, which is 55.14, leaving −6.97; add 0.4275 × 20 × 1.5424, which is 13.19, giving 6.22, which rounds to the calculator’s 6°F. The same arithmetic in Celsius uses the metric form of the formula, and the calculator’s Celsius mode is exactly that form, not a Fahrenheit answer converted after the fact.
| Condition | What the calculator does |
|---|---|
| Temperature above 50°F (10°C) | Wind chill is not defined; the calculator shows the actual temperature honestly |
| Wind below 3 mph | Wind chill is essentially the air temperature; calm air does not bite |
| Wind above 110 mph | Outside the formula’s tested range; the number is an extrapolation |
| Cars, pipes and objects | Wind cools them to the air temperature faster, never below it; wind chill does not apply |
| Sunshine | The formula assumes no sun; strong sun on exposed skin feels warmer than the wind chill |
The objects row deserves emphasis because it is the most common misunderstanding. A car radiator at −10°F in a 30 mph wind will reach −10°F faster than in calm air, but it will never reach the −39°F wind chill, because wind chill is a rate of heat loss from warm skin, not a temperature that the air itself attains. The same applies to pipes, engines and thermometers: the wind chill number is about living skin, and every other use of it is a metaphor that breaks if pushed.
New guide: Wind Chill Explained: The Formula, Chart, and How It Affects the Body
Wind chill is the temperature the air feels like on exposed skin, when wind strips away the thin layer of warm air the body heats around itself.
Wind chill is calculated from air temperature and wind speed with the 2001 National Weather Service formula, valid at or below 50°F (10°C) and at wind speeds above 3 mph. Outside that range the formula is not applied. The full guide, Wind Chill Explained: The Formula, Chart, and How It Affects the Body, works through the method in detail, with worked examples and the cases that most often go wrong.
Frequently asked questions
What is wind chill?
Wind chill is the temperature your exposed skin feels when wind is added to cold air. Moving air strips away the thin layer of warmth your body maintains next to the skin, so heat leaves faster and the cold bites harder than the thermometer suggests. A calm 20°F and a windy 20°F are the same air temperature but very different experiences; on this page, the windy one feels like 6°F.
How is wind chill calculated?
With the formula adopted by the National Weather Service and Environment Canada in 2001: wind chill = 35.74 + 0.6215T – 35.75V^0.16 + 0.4275TV^0.16, where T is the air temperature in °F and V the wind speed in mph. It applies only when T is at or below 50°F and V is at least 3 mph, and the answer is rounded to the nearest whole degree. Try it: 20°F at 15 mph gives 6°F.
Why does the calculator sometimes show my actual temperature?
Because outside its defined range there is no wind chill to calculate. The formula holds only at or below 50°F (10°C) with wind of at least 3 mph (4.8 km/h). Warmer than that, or in calm air, wind does not pull your skin below the air temperature in the way the model describes — so the page shows the actual temperature and tells you, rather than printing a number the science does not support.
How quickly can frostbite happen?
The National Weather Service puts exposed skin on a clock once the wind chill reaches its bands: about 30 minutes at -18°F (-28°C) or colder, about 10 minutes at -32°F (-36°C) or colder, and about 5 minutes at -48°F (-44°C) or colder. Cheeks, ears, nose and fingers freeze first. The times are guidance for an average adult; wet skin, poor circulation and alcohol all shorten them.
Does wind chill affect cars, pipes and objects?
Only partly. Wind makes a warm object cool to the air temperature faster, but no amount of wind can push an object below the air temperature itself — your radiator cannot reach the wind chill, only the thermometer reading. That is why antifreeze is rated to actual temperatures, why pipes freeze based on real temperature and exposure time, and why wind chill forecasts are written for skin, not machinery.
Is there a wind chill formula in Celsius?
Yes — Environment Canada publishes the metric form of the same model: 13.12 + 0.6215T – 11.37V^0.16 + 0.3965TV^0.16, with T in °C and V in km/h, defined at or below 10°C with wind of at least 4.8 km/h. The toggle at the top of this calculator switches to it. On the same weather the two forms agree to within about a degree: -10°C at 20 km/h gives -18°C, the twin of the Fahrenheit examples above.
How do I convert mph to km/h, m/s and knots?
Multiply miles per hour by 1.609344 for km/h, by 0.44704 for m/s, and by 0.868976 for knots. So 15 mph is 24.1 km/h, 6.7 m/s and 13.0 knots. The Advanced options panel converts your wind speed into all four at once, and its unit select switches the whole calculator between Fahrenheit/mph and Celsius/km/h.
What are Environment Canada’s wind chill risk categories?
Environment Canada publishes six bands in Celsius: 0 to −9 Low, −10 to −27 Moderate, −28 to −39 High (exposed skin can freeze in 10 to 30 minutes), −40 to −47 Very high (5 to 10 minutes), −48 to −54 Severe (2 to 5 minutes), and −55 or colder Extreme (under 2 minutes). The Advanced options panel shows which band your wind chill falls into.
Why does wet skin feel so much colder in wind?
Wind chill is the rate at which moving air strips away the warm layer next to the skin, and evaporation adds a second cooling mechanism on top of it. Wet skin, wet gloves or a wet scarf therefore lose heat far faster than dry skin at the same wind chill, which is why staying dry is as important as staying covered.
What should I wear when the wind chill is −30°F or colder?
Cover every patch of exposed skin, including face, ears and hands, since those freeze first; wear layers that trap still air with a windproof outer shell to keep that air still; and keep gloves and scarves dry. At those values the frostbite clock is 30 minutes or less, so limit time outside, go out in pairs where possible, and check each other for numb or waxy patches.
What is wind chill?
The temperature the air feels like on exposed skin when wind strips away the warm layer the body heats around itself. It is calculated from air temperature and wind speed with the National Weather Service formula, and it expresses heat loss from skin, not the temperature of the air.
Can wind chill make things colder than the air temperature?
No. Objects with no heat of their own cool to the air temperature and no further, however hard the wind blows. Wind only makes them reach air temperature faster. Wind chill applies to exposed skin, which the body keeps warm.
Does wind chill apply above 50°F?
No. The formula is not applied above 50°F (10°C), because wind has little chilling effect in warmer air, and the model was built for cold conditions. Wind speeds of 3 mph or less are also outside the formula’s range.
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→Wind Chill Explained: The Formula, Chart, and How It Affects the Body
Wind does not make the air colder — it strips away the warm layer your body heats around itself. This guide explains the NWS wind chill form
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