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Percentage Calculator

Calculators & Converters

Four percentage operations in one tool: X% of Y, X is what % of Y, % change from A to B, and add/subtract a percentage from a value.

Runs entirely in your browser
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About Percentage Calculator

Percentages come up everywhere — tipping, sales tax, discounts, growth rates, statistics — and the math is often simpler than the mental gymnastics required. This calculator splits the common operations into four tabs so you can pick the question that matches your situation and get the answer without manually re-deriving the formula.

'X% of Y' is the basic forward calculation (what's 15% of $200?). 'X is what % of Y' is the reverse (what percentage is $30 of $200?). '% change A → B' tells you growth or decline (revenue went from $100 to $125 — that's 25%). 'Add / subtract %' applies a markup or discount in both directions (a $100 item with 18% added is $118, with 18% off is $82). Each mode shows the math directly and includes a Copy button for the result. Everything runs in your browser.

How to use

  1. 1

    Pick the operation

    Click one of the four tabs: 'X% of Y', 'X is what % of Y', '% change A → B', or 'Add / subtract %'.

  2. 2

    Enter values

    Type into the labeled inputs. The result updates as you type.

  3. 3

    Copy the result

    Each result card has a Copy button.

Examples

Tip calculation: 18% of $84.50

X% of Y mode.

Input

X = 18, Y = 84.50

Output

15.21

Sales growth: from 1,200 to 1,560

% change mode tells you the percentage increase.

Input

A = 1200, B = 1560

Output

30% increase

Adding sales tax: $250 + 8.25%

Add/subtract mode shows both the +% and −% results.

Input

Value = 250, Percent = 8.25

Output

+%: 270.625 · −%: 229.375

Frequently asked questions

When should I use 'X% of Y' vs 'X is what % of Y'?+

Use 'X% of Y' when you know the percentage and want the absolute number ('what's 18% of $250?'). Use 'X is what % of Y' when you have two absolute numbers and want the ratio ('what percentage is $45 of $250?').

How does the % change mode handle decreases?+

Going from $100 to $75 is a −25% change (negative percentages indicate decrease). Going from $100 to $200 is +100%.

Why does add/subtract show both results?+

Most percentage adjustments come in pairs — a 20% markup and a 20% discount, sales tax added and a refund removed. Showing both prevents the common mistake of needing one direction and recalculating in your head.

Are the calculations exact?+

They use JavaScript's built-in number type (IEEE 754 double precision). Results are accurate to about 15 significant digits, more than enough for everyday percentages.

Is anything sent to a server?+

No. All math runs in your browser.

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