Percentage Calculator
Six percentage calculations on one page — X% of a value, what percent of what, change, difference, add or take off a percent, work back to the original.
🔒 Calculated live in your browser — nothing is uploaded.
Everyday percentage maths
Six calculators in one: a percentage of a value (15% of 200), what percent one number is of another (30 is what % of 200), percentage change between two numbers (200 → 250 = +25%), percentage difference, adding or taking off a percentage, and working back to the number before a percentage was applied. Each result updates live as you type. Everything runs in your browser.
Percentage change
Percentage change is the difference divided by the starting value, so going from 200 to 250 is +25%, and 250 back to 200 is −20% (the base changes, so the percentages differ).
Change and difference are not the same question
Percentage change has a direction: it measures from a starting value, so 200 → 250 is +25% while 250 → 200 is −20%. The same gap, two different numbers, because the base moved. Percentage difference compares two values with no before and after, dividing by their average instead, so it gives one answer whichever order you put them in — 22.2% for that pair. Use change for anything over time: a price, a salary, a reading. Use difference when neither value is the reference: two measurements of the same thing, two quotes, two results.
Percent, percentage points, and why a fall needs a bigger rise
A rate going from 4% to 6% has risen by two percentage points and by 50 percent. Both are true and they are not the same statement; news copy mixes them constantly. The other trap is that percentages do not cancel. Lose 50% and you need +100% to get back, because the rise is measured from the smaller number. A 20% discount followed by a 20% rise leaves you at 96% of where you started, and stacking two discounts of 20% and 10% gives 28% off, not 30% — the second is taken from what the first left.
Frequently asked questions
What is percentage change?
It measures how much a value grew or shrank relative to its starting point: (new − old) ÷ old × 100.
Why is an increase then decrease not symmetric?
Because the base differs. +25% from 200 is 250, but −20% from 250 returns to 200 — the same amount is a different percentage of a different base.
Is anything uploaded?
No. Calculations run entirely in your browser.
Change or difference — which do I want?
Change, if one value came before the other and you care about the direction. Difference, if they are two readings of the same kind of thing and neither is the baseline. Difference is order-independent; change is not.
Why does −50% then +50% not return to the start?
Because each percentage is taken from a different base. 100 falls to 50, then 50% of 50 is 25, so you land at 75. Recovering from −50% takes +100%.
Is 2 percentage points the same as 2 percent?
No. Going from 4% to 6% is a rise of two percentage points and of 50 percent. Points compare rates directly; percent compares them relatively.