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Percentage calculator

Work out X % of Y, percentage share, percentage change and discounted prices, with the formula shown.

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Percentage calculator
Percentages show up everywhere — a maths worksheet, a 15 % tip, VAT on an invoice, a price cut in a sale — and each situation asks the question a slightly different way. This calculator covers the four everyday forms. Pick the calculation, type X and Y, and the answer appears instantly, followed by the formula with your numbers substituted, so you can see how it was reached and copy the working into homework or a spreadsheet.
X % of Y answers the most common case: 20 % of 150 is 30 — a tip on a bill, VAT on a net price, a commission on a sale. X is what % of Y turns it around: score 42 points out of 60 and you get 70 %. Change from X to Y measures growth or decline between two values and labels the result as an increase or a decrease — handy for price rises, follower counts and year-on-year comparisons. Y after X % discount does sale-price arithmetic in one step: 150 after a 20 % discount is 120.
Numbers are formatted for the active language, so decimal commas and thousands separators come out right, results are rounded to at most four decimal places, and negative values work in every mode. Impossible questions — what percentage of zero, a change starting from zero — get a plain explanation instead of a cryptic error.
Everything runs in your browser. The numbers you type never leave your device, which makes the calculator safe for invoices, salaries and grades alike.
FAQ
How do I work out X % of Y?
Multiply Y by X divided by 100: 20 % of 150 is 150 × 0.2 = 30. Pick the "X % of Y" calculation, enter both numbers and the tool prints the answer with that formula written out.
How is the percentage change calculated?
The "Change from X to Y" mode uses (Y − X) ÷ X × 100. From 120 to 150 that gives +25 %, an increase; from 150 to 120 it gives −20 %, a decrease.
Why do I get an error when Y is 0?
Asking what percentage a number is of zero means dividing by zero, which has no defined answer. The same applies to a change starting from 0. Enter a non-zero base value instead.
Are the numbers I enter uploaded anywhere?
No. The calculator runs entirely in your browser and nothing you type leaves your device — safe for salaries, invoices and grades.