Percent Change Calculator

Enter a starting value and an ending value to see how much it changed in percent and in absolute terms, plus the symmetric percent difference for when neither number is the "starting" one.

Percent increase
25%
80 → 100
Absolute change
+20
Percent difference
≈ 22.2222%symmetric: same whichever value comes first
New ÷ old
1.25×
To get back to 80
decrease by 20%
  • Step 1, absolute change: new − old = 100 − 80 = 20.
  • Step 2, divide by the starting value: 20 ÷ 80 = 0.25.
  • Step 3, multiply by 100 to get a percentage: 25%. Positive, so it's an increase.
  • Percent difference (no direction): the gap is |100 − 80| = 20; the average of the two is (80 + 100) ÷ 2 = 90; 20 ÷ 90 × 100 ≈ 22.2222%.
  • Going back is a different percentage, because it's measured from the new value: (80 − 100) ÷ 100 × 100 = -20%.

Percent change vs. percent difference

Percent change has a direction. It compares a new value with an old one and measures the change relative to the old value: going from 80 to 100 is a 25% increase. Use it for anything over time — prices, salaries, populations, test scores from one term to the next. The U.S. Bureau of Labor Statistics calculates inflation from the Consumer Price Index the same way: (later value − earlier value) ÷ earlier value × 100.

Percent difference has no direction. It compares two values on an equal footing by dividing the gap by their average: 80 and 100 differ by 20 ÷ 90 × 100 ≈ 22.22%, whichever you list first. Use it when neither number is the baseline, such as two lab measurements of the same thing or the prices of the same item at two stores.

Why a rise and a fall don't cancel out

Percent changes are measured from different starting points, so they aren't symmetric. A rise from 80 to 100 is +25%, but the fall from 100 back to 80 is −20%, because the second change is measured from 100. That's why a stock that drops 50% needs a 100% gain to get back to where it started.

For the same reason, you can't add percent changes. Two years of 10% growth is 1.1 × 1.1 = 1.21, a 21% increase, not 20%.

Percent vs. percentage points

When the values are already percentages, say which change you mean. An interest rate going from 4% to 5% rose by 1 percentage point, but by 25% in relative terms. Both are correct; mixing them up is one of the most common errors in news reports and presentations.

For other percentage questions — what is 15% of 80, or what percent 12 is of 80 — use the percentage calculator.

Formulas

Percent change = (new − old) ÷ |old| × 100Absolute change = new − oldPercent difference = |a − b| ÷ ((|a| + |b|) ÷ 2) × 100
  • old = starting value (can't be 0); new = ending value
  • a, b = the two values being compared when neither is the baseline
  • |x| = the size of x, ignoring any minus sign

Worked example: a price rises from $80 to $100

  1. Absolute change: 100 − 80 = 20.
  2. Percent change: 20 ÷ 80 = 0.25, and 0.25 × 100 = 25% increase.
  3. Going back from 100 to 80: (80 − 100) ÷ 100 × 100 = −20%, a 20% decrease.
  4. Percent difference: the average of 80 and 100 is 90, so 20 ÷ 90 × 100 ≈ 22.22%.

Frequently asked questions

How do I calculate a percentage decrease?

Use the same formula: (new − old) ÷ old × 100. The result is negative for a decrease. A price falling from $50 to $40 is (40 − 50) ÷ 50 × 100 = −20%, a 20% decrease.

Can percent change be more than 100%?

Increases can: going from 20 to 50 is a 150% increase. Decreases can't go beyond −100% for positive values, because −100% means the value fell to zero.

What if the starting value is zero?

Percent change is undefined, because you'd be dividing by zero. Report the absolute change instead, for example "up from 0 to 12".

Which should I use, percent change or percent difference?

Use percent change when one value clearly comes first or is the reference, such as before and after. Use percent difference when the two values are peers, such as two measurements of the same quantity.

If something grows 10% two years in a row, is that 20%?

No. Each year's growth builds on the last: 1.10 × 1.10 = 1.21, so the total increase is 21%.

Sources

Last reviewed for 2026. How we calculate.