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Percentage Calculator

Pick the question you are actually asking — the fields and the answer change with it. Every calculation updates as you type, and the sentence under the result shows how the numbers fit together.

Result

How to use

  1. Choose the tab that matches your question, from “% of a number” to “find the original number”.
  2. Fill in the two fields — their labels change with the tab, so you always know which number goes where.
  3. Read the answer above the explanation; it recalculates on every keystroke.
  4. Switch tabs to ask the reverse question about the same numbers.

Good to know

Increase and decrease are not symmetrical

A price that rises by 50% and then falls by 50% does not come back to where it started — it ends 25% lower. The percentage is always taken from the current number, which is why “+20% then −20%” is a loss, not a wash.

Removing a tax is not subtracting a percentage

If a price includes 20% tax, the net price is not “price minus 20%”. The tax was added to the smaller number, so you have to divide: use “find the original number” with 120 as the percentage. On 1200 that gives 1000, while subtracting 20% would wrongly give 960.

Percent, percentage point, and why the difference matters

If a rate moves from 4% to 5%, that is one percentage point but a 25% increase. Both statements are true and they describe the same change; news and contracts routinely swap one for the other, and the gap between them can be large.

Frequently asked questions

How do I work out a discount?

Use “subtract a percentage”: the number is the original price and the percentage is the discount. To find the discount from two prices, use “increase or decrease”.

How do I add VAT or sales tax?

Use “add a percentage”. To go the other way — from a price with tax to the price without — use “find the original number” with 100 plus the rate as the percentage.

What is X as a percentage of Y?

That is the “X is what % of Y” tab: the first field is the part, the second is the whole.

Why does a change from zero give no answer?

Percentage change is measured against the starting value, and nothing can be a percentage of zero. The tool says the result is undefined rather than showing infinity.

How is a change from a negative number handled?

The change is measured against the size of the starting number, so a move from −100 to −50 is shown as +50%: the value went up, and the sign of the answer says so.

Are the numbers sent anywhere?

No. Everything is calculated in your browser, so salaries, prices and any other figures stay on your device.

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