Percent Change Calculator
Free percentage change calculator: find the percent increase or decrease between two numbers, plus the percent difference.
Last reviewed: July 2026Percent difference is a symmetric measure — it divides the gap by the average of the two values — so it is not the same as percent change.
Quick Answer
Percent change is the difference between two numbers as a share of the starting value: subtract the old value from the new value, divide by the starting value, and multiply by 100. Going from 80 to 92 is a change of +12, and 12 ÷ 80 = 15%, a 15.00% increase.
What This Calculator Does
This calculator finds the percent change between a starting value and an ending value: the increase or decrease from one number to another, measured against the number you started with. Alongside the headline percentage, it reports the absolute change (the raw difference), the percent difference (a symmetric measure that does not treat either number as the baseline), and the ending value expressed as a percentage of the starting value. It is built for the one question the general percentage calculator does not center on: how much did a value go up or down, in relative terms? If you instead need to find a percentage of a number, or work out what percent one number is of another, reach for that general tool. Here, the starting value is always the baseline, and every result is measured from it.
How to Use It
Enter your starting value and your ending value in the two fields above. Results update as you type — there is no button to press. The headline shows the signed percent change and whether it is an increase or a decrease; below it, the absolute change and percent difference appear side by side, and a short sentence expresses the ending value as a percentage of the starting value. Leave a field blank and the results clear, so a half-entered calculation never shows a misleading number. Your two values are written into the page URL as you go, so the Share button copies a link that reproduces the exact calculation for anyone who opens it. Reset returns the fields to 80 and 92, and Print produces a clean copy of the result for your records.
Worked Examples
Every number below can be reproduced in the calculator above.
A rise from 80 to 92
The absolute change is 92 − 80 = +12. Dividing by the starting value gives 12 ÷ 80 = 0.15, so the percent change is +15.00%, an increase. The ending value is 115.00% of the starting value.
A fall from 250 to 200
The absolute change is 200 − 250 = −50. Dividing by 250 gives −50 ÷ 250 = −0.20, a −20.00% decrease.
Why 50% up then 50% down does not return to the start
Start at 100 and add 50%: 100 becomes 150. Now take 50% off 150 and you get 75, not 100, because the second percentage is measured from 150. To move from 150 back to 100 you need a decrease of only −33.33%.
Percentage points versus percent
A rate that moves from 4% to 5% has risen by 1 percentage point. As a relative change, though, that same move is +25.00%, because 1 ÷ 4 = 0.25. The arithmetic gap and the relative change describe the same step in different units.
Percent difference between 40 and 60
Percent difference divides the gap by the average: |40 − 60| ÷ 50 = 20 ÷ 50 = 40.00%. It does not depend on order. Percent change does: 40 to 60 is +50.00%, while 60 to 40 is −33.33%. That contrast is the clearest way to see why the two measures are not interchangeable.
A negative starting value: −20 to 10
The absolute change is 10 − (−20) = +30. Because the formula divides by the absolute value of the start, the denominator is |−20| = 20, so the percent change is 30 ÷ 20 = +150.00%, an increase.
Percent Change vs. Percent Difference vs. Percentage Points
These three measures answer different questions, and choosing the wrong one is a common source of confusion.
Percent change needs a baseline. It measures how far the ending value moved from the starting value, as a share of the start, so it is directional: 40 to 60 is +50.00%, but 60 to 40 is −33.33%. Use it whenever one value is clearly “before” and the other is “after” — last year versus this year, original price versus sale price, old salary versus new salary.
Percent difference is symmetric. It divides the gap between two numbers by their average, so neither number is privileged and the order does not matter: 40 and 60 differ by 40.00% whichever way you read them. Use it to compare two measurements when there is no natural baseline — two lab readings, two estimates, two sensors.
Percentage points apply when the two numbers are themselves percentages. Moving from 4% to 5% is a rise of 1 percentage point, and that is the honest way to describe it; calling it a +25.00% change is also true but measures something different. When you compare rates or shares, say percentage points to keep the units clear.
Common Mistakes
Dividing by the wrong value
Percent change always divides by the starting value. For the rise from 80 to 92, the change of 12 is divided by 80, not by the ending value of 92. Dividing by 92 answers a different question and produces a smaller, wrong figure. If a result looks too flattering or too harsh, check which number is in the denominator first.
Assuming equal percentages cancel
A 50% increase followed by a 50% decrease does not return you to the start. From 100 you rise to 150, then fall to 75 — a net loss — because each step is measured from a different number. Gains and losses of the same percentage never cancel; the second one is applied to a larger or smaller base than the first.
Confusing percentage points with percent
When a rate goes from 4% to 5%, that is 1 percentage point, not “1%”. As a relative change it is +25.00%. Mixing the two units turns a one-point move into an alarming-sounding jump, or hides a real one. Decide which unit you mean before you report it.
The Formula, Step by Step
Percent change is defined as:
percent change = (new − old) ÷ |old| × 100
The vertical bars mean “absolute value” — the size of the starting number, ignoring its sign. Working the rise from 80 to 92 through the formula, step by step:
- Subtract to get the absolute change: 92 − 80 = 12.
- Divide by the absolute value of the starting number: 12 ÷ |80| = 12 ÷ 80 = 0.15.
- Multiply by 100 to turn the fraction into a percentage: 0.15 × 100 = 15, shown as +15.00%.
The absolute value in the denominator is what lets negative starting values behave sensibly. Going from −20 to 10, the denominator is |−20| = 20 rather than −20, so a move upward is reported as a +150.00% increase instead of flipping to a negative sign. When the starting value is 0 there is nothing to divide by, and the percent change is undefined — that is the one input the formula cannot handle, and the absolute change is the number to use instead.