Calculate percent change, percent difference, or increase or decrease a number by a given percentage with formulas shown.
%
Percent change
Magnitude comparison
a = 200b = 250
(250 − 200) / 200 × 100 = +25%
Quick reference: percent change from 100
From → To
% change
% difference
100 → 110
+10%
9.52%
100 → 125
+25%
22.22%
100 → 150
+50%
40.00%
100 → 200
+100%
66.67%
100 → 90
−10%
10.53%
100 → 75
−25%
28.57%
100 → 50
−50%
66.67%
100 → 20
−80%
133.33%
Frequently asked questions
What is the difference between percent change and percent difference?
Percent change compares a new value to a known reference (old): (b − a) / a × 100. It is directional — increases are positive, decreases negative. Percent difference is symmetric and uses the average of both values as the reference: |b − a| / ((a + b) / 2) × 100. Use change for time-series and growth, difference when both values are equally valid measurements (e.g., two lab readings).
How do I calculate percent change between two numbers?
Subtract the old value from the new, divide by the old, then multiply by 100. Example: from 200 to 250 → (250 − 200) / 200 = 0.25 → +25%. The sign tells you direction: positive = increase, negative = decrease. If the old value is 0, percent change is undefined (you cannot grow by a percentage from zero).
Why does a 50% drop need a 100% gain to recover?
Because the base changes. 100 dropping by 50% leaves 50. To get back to 100, that 50 must double — an increase of 100%, not 50%. Percent change is asymmetric: a +x% followed by a −x% does not return to the start. This is why long-term returns compound rather than average linearly.
How is "increase by %" different from "percent change"?
"Increase by %" is forward: you have a and a rate p, and you compute b = a × (1 + p/100). Example: increase 200 by 25% → 250. "Percent change" is reverse: you have both a and b and compute the rate. The two operations are inverses.
When should I use percent difference instead of percent change?
Use percent difference when there is no "before" and "after" — both values are independent measurements you want to compare symmetrically. Common cases: comparing two experimental results, two prices on different sites, two answers from different methods. The formula divides by the mean, so swapping a and b gives the same answer.
Can percent change exceed 100%?
Yes, when the new value is more than double the old. From 100 to 250 is +150%, from 100 to 1000 is +900%. Percent decrease, however, cannot exceed 100% — the smallest a positive value can become is 0, which is −100%. Percent difference is bounded between 0% and 200%.
Are percentage points the same as percent?
No. Percentage points measure the absolute gap between two percentages. If a rate goes from 4% to 6%, that is a 2 percentage-point rise but a 50% relative increase. Headlines often confuse these. The calculator above operates on raw numbers; if your inputs are already percentages, the result is in percentage points relative to the original rate.
Results round to two decimals. Use additional decimal places in the input fields when precision matters.
Compute the percent change, the percent difference, or apply a percentage increase or decrease to any number in four clicks. Pick a mode — Percent change (a→b) for directional growth or decline, Percent difference for symmetric comparison around the mean, Increase by % to project a value forward, or Decrease by % to apply a discount or rate cut. The result shows the formula, signed direction, the absolute delta, and a magnitude bar comparing the two values. A quick-reference table covers the most common cases from +10% to −80% so you can sanity-check at a glance. Examples: 200 to 250 is a +25% change but a 22.22% difference. A 50% drop needs a 100% gain to recover, because the base shifts. A 10-percentage-point move from 4% to 14% is a 250% relative increase. Use percent change for time-series, percent difference when both values are equally valid measurements, and the increase/decrease modes when projecting forward.