Percentage Calculator

Four quick calculators in one: find a percentage of a number, work out what percent one number is of another, measure a percentage increase or decrease, and add or subtract a percentage. Results update as you type and everything runs in your browser — nothing is sent anywhere and nothing is stored.

What is X% of Y?

of

Enter values to see the result.

X is what percent of Y?

of

Enter values to see the result.

Percentage change from X to Y

to

Enter values to see the result.

Add or subtract a percentage

to

Enter values to see the result.

How to use the percentage calculator

  1. Pick the card that matches your question — each one works independently.
  2. Type your numbers into the fields; the result appears instantly, no button to press.
  3. Decimals like 12.5 and negative values like -40 are fully supported.

Quick formulas: X% of Y is Y × X / 100; X of Y as a percent is X / Y × 100; change from X to Y is (Y - X) / X × 100; add X% to Y is Y × (1 + X / 100). Dividing by zero shows a dash instead of a result.

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Frequently asked questions

How do I calculate X% of a number?

Multiply the number by the percentage divided by 100. For example, 20% of 150 is 150 × (20 / 100) = 30. In the first card, enter the percentage and the number and the result appears instantly.

How do I work out what percent one number is of another?

Divide the part by the whole, then multiply by 100. For example, 30 out of 150 is (30 / 150) × 100 = 20%. The second card does this for you as you type.

How do I calculate a percentage increase or decrease?

Subtract the old value from the new value, divide by the old value, then multiply by 100: ((new - old) / old) × 100. A positive result is an increase and a negative result is a decrease. The third card shows the signed percentage change.

How do I add or subtract a percentage from a number?

To add, multiply the number by 1 + percent/100; to subtract, multiply by 1 - percent/100. For example, adding 15% to 200 gives 200 × 1.15 = 230. The fourth card handles both.

Can I use decimals and negative numbers?

Yes. Every field accepts decimals (such as 12.5) and negative numbers (such as -40). Results update live and are rounded for display while keeping full precision internally.

Is my data sent anywhere?

No. All calculations run entirely in your browser — nothing is uploaded to a server and nothing is stored. You can even use the tool offline once the page has loaded.