Percentage Calculator
Free · no signup · runs entirely in your browser
Open the tool →A percentage calculator does one small job, and this one does it three ways. Mode one answers 'what is X% of Y?' — the tip, the discount, the 20% off a jacket. Mode two flips it: 'X is what % of Y?', which is the question you get when you have two numbers and no real sense of what the ratio between them means. Mode three handles percentage change from X to Y, shown signed — plus for an increase, minus for a decrease. Three modes. That is the entire tool, and we are not going to pretend there is a fourth.
You type numbers and the results appear. There is no calculate button to hunt for, no form to submit, and no waiting on a server to do arithmetic your phone could have handled in 1998. Everything runs in JavaScript inside your browser tab, which means nothing you type gets uploaded anywhere — not the numbers, not the salaries, not the invoice totals, not whatever it is you would rather not hand to a stranger's database. Close the tab and it is gone.
It is free. No signup, no account, no email capture, no 'create a free profile to unlock advanced modes'. No ads, and no tracking script logging which mode you clicked. The page loads once and then it is just maths. If you need statistics, compound interest, or an amortisation schedule, this is not that tool and you should go find one that specialises. But if you are standing in a shop working out 15% off, reconciling last quarter's numbers, or checking whether a rent increase is as bad as it feels, this covers it. It does the thing, in your browser, done.
How to use it
- Pick one of the three modes: 'What is X% of Y?', 'X is what % of Y?', or 'Percentage change from X to Y'.
- Type your two numbers into the fields — the result updates as you type, so there is no button to press.
- Read the answer. Percentage change comes signed: plus means an increase, minus means a decrease.
Worked example
Say a 240 euro jacket is 35% off. Use mode one, 'what is X% of Y?': X is 35, Y is 240, and you get 84 — that is the discount, so you pay 156. Now say the price drops again, from 156 to 140. Switch to mode three, percentage change from X to Y, enter 156 and 140, and you get -10.26% — a 10.26% drop. Same tool, two completely different questions, no mental arithmetic at the till.
FAQ
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number: (percent / 100) x number. So 20% of 60 is 0.2 x 60 = 12. That is what mode one does for you.
What is the percentage change formula?
((new value - old value) / old value) x 100. If the result is negative it is a decrease, if positive it is an increase. Mode three applies this and shows the result signed, so the direction is right there in the answer.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100: (X / Y) x 100. For example, 30 out of 120 is (30 / 120) x 100 = 25%. Mode two handles this one.
Is it free, and does anything I type get sent anywhere?
It is free, with no signup and no account. All three modes run in JavaScript in your browser tab, so the numbers you enter never leave your device — there is no server on the other end to send them to.
Open the Percentage Calculator →