Percent Increase Calculator — Percentage Change Between Two Values
From 80 to 120 is +50% — not 40%. Enter any starting value and new value to get the exact percentage change, the difference, and whether it is an increase or a decrease.
Two values
🔒 All calculations happen in your browser — no data leaves your device.
The change
The two values, to scale
The starting value and the new value drawn on one scale, with the change riding on top.
- From 80 to 120 is +50.00%, not 40% — the change (+40) is measured against the starting value, not the new one.
- The same run shows the difference (+40), the ratio (1.50×) and a plain-English verdict: 120 is 150% of 80.
- Second tool: apply a percentage — 250 increased by 15% is 287.50, decreased by 15% is 212.50, and the change amount is 37.50.
Second tool: apply a percentage
Know the percent and want the result? Raise or lower any value by a set percentage — both answers side by side.
Your value
Both ways
Keep exploring
Three companion tools for percentages and prices.
How it works
Three steps from two numbers to one percent.
Enter the starting value
Where things began — last year’s price, the old salary, the first measurement. The change is always measured from here.
Enter the new value
Where things ended up. It can be higher (an increase), lower (a decrease), or exactly the same (0.00%).
Read the change
The signed percentage change, the plain difference, and the ratio between the two values.
The math behind percentage change
Percentage change always answers one question: the difference compared to what? The answer is the starting value. Subtract the start from the new value, divide by the size of the starting value, and multiply by 100. A positive result is an increase, a negative result is a decrease — and because the base is always the start, the trip back is a different percent from the trip out.
Worked examples:
| Change | Calculation | Result |
|---|---|---|
| 80 → 120 | (120 − 80) ÷ 80 × 100 | +50.00% · difference +40 |
| 120 → 80 (the way back) | (80 − 120) ÷ 120 × 100 | −33.33% · difference −40 |
| 250 with 15% applied | 250 × 1.15 · 250 × 0.85 | Increased 287.50 · decreased 212.50 |
| 45 → 45 | (45 − 45) ÷ 45 × 100 | 0.00% · no change |
The starting value cannot be zero: a change from 0 has no base to divide by, so percentage change from zero is undefined — describe it in plain numbers instead (“grew from 0 to 50”).
Go deeper
Two traps that catch almost everyone at least once.
Because each percent is measured from a different base:
- Up 50%: 80 grows by half of 80 (+40) to reach 120.
- Down 50% from there: 120 falls by half of 120 (−60) to land on 60 — not back at 80.
- The true way back: returning from 120 to 80 is a fall of 40 on a base of 120, which is −33.33%.
- Investors live this: a holding that drops 50% needs a +100% gain just to break even. Losses and gains are never mirror images.
When the thing changing is itself a percent, two different ideas get confused:
- Percentage points are the plain subtraction: an interest rate moving from 5% to 6% rose by 1 percentage point.
- Percent change is relative: that same move is +20% relative to the starting 5%.
- Headlines mix them up: “rates up 20%” and “rates up 1 point” can describe the very same event — always check which one is meant.
- This calculator measures percent change between any two values, including two rates: enter 5 and 6 and it shows +20.00%.
Beyond one step: reversing a change, growth over years, and percentage points
One-step change is the start. Reversing it, chaining years, and naming points correctly are the rest.
Reversing a percentage change means dividing, not subtracting the percent. If a value rose by p percent to reach its new value, the original is the new value divided by 1 plus p over 100. A price that is 120 after a 20 percent rise started at 120 divided by 1.20, which is 100; subtracting 20 percent of 120 instead would give 96, which is wrong. The same division, with a minus sign, reverses a fall: a value that fell by p percent to reach its new value started at the new value divided by 1 minus p over 100. Always show the plain difference next to the reversed figure, so the reader can see the change as well as the percent.
Growth over several years compounds, year by year. A value that grows 10 percent in one year and 10 percent in the next does not grow 20 percent in total: 100 becomes 110, and then 110 grows by 10 percent to 121, a total rise of 21 percent. Year-over-year growth is each year change measured against the previous year, not against the first year, which is why the yearly percentages cannot simply be added. The single yearly rate that produces the same total over the whole period is the compound annual growth rate: the end value divided by the start value, raised to the power of 1 over the number of years, minus 1. For 100 growing to 121 over 2 years, that is the square root of 1.21 minus 1, which is 10 percent a year. Use year-over-year figures to describe each year, and the compound rate to describe the period as a whole.
Percentage points, covered in the accordion above, stay a separate idea from percent change even here: a rate moving from 20 percent to 25 percent rose by 5 percentage points, which is a 25 percent relative rise. When the values being compared are themselves percentages, name which one you mean in the same sentence as the number, or the reader cannot tell whether 5 points or 25 percent was meant. Percent difference, which treats neither value as the base, is a different comparison again, and is worked through on the Percentage Calculator page.
Frequently asked questions
Quick answers about percentage change.
How do I calculate percent increase?
Subtract the starting value from the new value, divide by the starting value, and multiply by 100. From 80 to 120: (120 − 80) ÷ 80 × 100 = +50.00%. The sign tells the story: positive is an increase, negative is a decrease.
What is the percent change from 80 to 120?
+50.00%. The difference is 40, and 40 measured against the starting value of 80 is exactly one half — a 50% increase. The new value is 1.50× the starting value, or 150% of it.
How do I calculate a percent decrease?
Exactly the same way — the result simply comes out negative. From 120 down to 80: (80 − 120) ÷ 120 × 100 = −33.33%. One formula covers both directions, which is why this calculator reports a signed percentage change.
What is a 15% increase on 250?
287.50. Fifteen percent of 250 is 37.50, so increasing gives 250 + 37.50 = 287.50, and decreasing by the same 15% gives 250 − 37.50 = 212.50. The second tool on this page works out both directions at once.
Why is the increase from 80 to 120 not 40%?
Because 40 is the difference, not the percent. A percent always compares the difference to the starting value: 40 out of 80 is one half, so the increase is 50%. If the same +40 happened from a start of 400, it would be only +10% — the base decides.
Can percent change be more than 100%?
Yes — on the way up there is no limit. Doubling is +100%, tripling is +200%, and growing from 10 to 1,000 is +9,900%. Decreases are the capped direction: a value cannot fall more than 100% without going below zero.
What is the difference between increased by 20% and increased to 120%?
They describe the same event. Increasing 250 by 20% adds 50 to reach 300, and 250 increased to 120% of itself is also 300, because 120% of 250 is 300. By contrast, 20% of 250 is just 50, a part of the original, not a new total.
What happens with a negative starting value?
The calculator uses the size of the starting value as the base, so moving from −50 to −30 is reported as +40%: the value rose by 20, and 20 is 40% of the starting value’s size of 50. Read it as ‘the value rose’ rather than as growth, and always show the plain difference next to the percent.
How do I reverse a percentage increase?
Divide the new value by 1 plus the percent over 100. A price that is 120 after a 20 percent rise started at 120 divided by 1.20, which is 100. Do not subtract the percent from the new value: subtracting 20 percent of 120 gives 96, which is wrong. To reverse a fall, divide by 1 minus the percent over 100, and always show the plain difference next to the result.
How do I calculate percentage growth over several years?
Work year by year: each year growth is measured against the previous year, and the yearly percentages compound rather than add. Growing 10 percent and then 10 percent again takes 100 to 121, a total rise of 21 percent, not 20 percent. The compound annual growth rate is the end value divided by the start value, raised to the power of 1 over the number of years, minus 1: for 100 to 121 over 2 years, that is 10 percent a year.
Increase, decrease, or just a percent of a number?
Three questions that sound alike, with three different answers — and the table that keeps them apart.
A percent increase, a percent decrease, and a percent of a number are three different questions, and the calculator on this page answers the first two. The third belongs to the companion Percentage Calculator, but the distinction is worth stating here because the searches mix them freely. Twenty percent of 250 is 50 — a part sitting inside the original. Increasing 250 by 20% adds that 50 and lands on 300. Decreasing 250 by 20% subtracts 50 and lands on 200. And increasing 250 to 120% of itself is also 300, because 120% of 250 is 300. Same percent, same starting value, three different results — and the wording (of, by, to) is the only thing telling them apart.
| Question about 250 | Calculation | Answer |
|---|---|---|
| 20% of 250 | 250 × 0.20 | 50 (a part) |
| 250 increased by 20% | 250 × 1.20 | 300 |
| 250 decreased by 20% | 250 × 0.80 | 200 |
| 250 increased to 120% | 250 × 1.20 | 300 |
Negative starting values deserve the same plain treatment. The calculator uses the size of the starting value as its base, so moving from −50 to −30 is reported as +40%: the value rose by 20, and 20 is 40% of the starting value’s size of 50. Read that as “the value rose”, not as growth in the usual sense, and always show the plain difference next to the percent when a starting value can be negative. The companion guides below work the full set of cases — increase versus decrease, percentage points, raises, prices, and growth — with every base named.
Related guides
Deeper reading on percent change, from this page’s own guides.
Related calculators
More tools for percentages, prices and margins.
Disclaimer
This calculator is for information only. Percentage change is undefined when the starting value is zero, and results are exact arithmetic on the numbers you enter — rounding in source figures (prices, rates, statistics) can shift the final percent slightly. Double-check consequential figures against the original data.