Percentage Calculator

Solve everyday percentage questions in four modes — no formulas to remember.

Percentage (%)

Of value

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🔒 Nothing you enter is sent anywhere or stored. All processing happens in your browser.

How it works

Percentages express a part of a whole out of 100, but the same word covers several different questions. This calculator handles the four most common ones so you don't have to remember which formula applies.

X% of Y answers "what is 20% of 150?" by computing X ÷ 100 × Y. X is what % of Y reverses that — it tells you what proportion one number is of another, using X ÷ Y × 100, perfect for working out a score or a share. Percentage increase and percentage decrease compare an original value to a new one and report how much it changed relative to the starting point, using (new − old) ÷ old × 100.

The distinction between increase and decrease matters: a change is always measured against the original figure, so a rise from 40 to 50 is a 25% increase, while a fall from 50 to 40 is a 20% decrease — the same 10-unit gap gives different percentages because the baselines differ. Results update as you type, and you can copy any answer with one click.

Examples

20% of 150 = 30

45 is what % of 60? = 75%

Increase from 40 to 50 = 25%; decrease from 50 to 40 = 20%

Frequently asked questions

Why are increase and decrease percentages different for the same numbers?

Because each is measured against its own starting value. Going 40→50 is +25% (10 out of 40), while 50→40 is −20% (10 out of 50). The baseline changes, so the percentage does too.

How do I find what percentage one number is of another?

Use the 'X is what % of Y' mode: it divides X by Y and multiplies by 100. For example, 45 out of 60 is 75%.

Can it handle decimals and negative numbers?

Yes. You can enter decimal values, and increase/decrease modes accept negative results when a value drops below zero.

Is my input stored?

No. The calculation runs in your browser and nothing you enter is saved or transmitted.