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Percentage Calculator

Percent of a number, ratios and change

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-12
Free Private No uploads
What is Percentage Calculator?

Percentages get vague because the same word covers three different questions, so this tool asks you to pick which one you mean. What is X percent of Y divides X by 100 and multiplies by Y, and it writes the substitution out so you can follow it. X is what percent of Y divides X by Y and multiplies by 100, with a guard that stops the result from blowing up when Y is zero. Percentage change from X to Y divides the difference by the absolute value of the starting figure, so a drop from 200 to 150 reads as a 25 percent decrease rather than a misleading negative increase. Every mode shows the formula it used underneath the answer, which matters more than it sounds when a spreadsheet is telling you something different.

Solve every common percentage question: X% of a number, what percent one number is of another, and percentage increase or decrease — with the formula shown for each result.

Private Percentage Calculator In Your Browser

Percentage Calculator is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use Percentage Calculator

1

Choose the question type: `What is X% of Y?`, `X is what % of Y?`, or `Percentage change from X to Y`.

2

Enter the first figure in Value A and the second in Value B.

3

Read the highlighted answer, plus the formula line showing the substitution with your own numbers in it.

4

In change mode, check the absolute change row as well — the percentage alone hides the size of the move.

Key Capabilities
  • Three distinct percentage questions share one pair of inputs instead of making you retype numbers for each.
  • Each answer is accompanied by the formula with your own values substituted, so you can check the working rather than trust the number.
  • Percentage change divides by the absolute value of the starting number, which makes a decrease and an increase comparable in one reading.
  • Dividing by zero is caught in both ratio and change modes and reported as an error instead of returning infinity.
Common Use Cases
  • A buyer works out whether a supplier's quote including 20 percent VAT beats last quarter's quote.
  • A warehouse lead calculates headcount up or down after a reorganisation, moving from 34 staff to 29.
  • An analyst sanity-checks a growth figure in a report before quoting it to a client.
Clear Answers

Frequently Asked Questions

Why does a fall from 200 to 150 show as 25 percent and not 0.75 percent?
The magnitude is what matters, so the tool divides the 50-unit drop by the original 200 and reports 25 percent decrease. Sign is carried in the wording — Increase or Decrease — rather than in the number itself.
What does 15 percent of 200 give?
30, with the formula line reading 15% × 200 = 0.15 × 200 so the division by 100 is visible.
Can I work out a percentage increase and then apply it?
Yes, in two steps. Take the increase in change mode, then enter that percentage in `What is X% of Y?` against the original figure.
Does it handle percentages above 100?
Yes. A value of 150 percent is just 1.5 times the second figure, and the percentage-change mode will happily return changes far larger than 100 percent.

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