How do I calculate x% of y?

Convert x to decimal (x ÷ 100) then multiply by y. Example: 15% of 200 = 0.15 × 200 = 30.

How is percent change calculated?

Percent change = ((new − old) ÷ old) × 100. Use a negative result to indicate a decrease.

If the current value is after a p% increase, original = current ÷ (1 + p ÷ 100).

Operation

Value A

Value B

Percent (p)

Decimal precision

Choose how many digits appear after the decimal point (0–12).

Choose an operation and enter the values, then press Calculate.

Clear explanations and practical examples to help you apply percentage math in finance, data, and everyday situations.

To compute x% of y, convert the percent to a decimal (x ÷ 100) and multiply by y. Example: 15% of 200 = 0.15 × 200 = 30.

To find what percent a is of b, compute (a ÷ b) × 100. Example: 50 is what percent of 200? (50 ÷ 200) × 100 = 25%.

Percent change from old value a to new value b is ((b − a) ÷ a) × 100. Positive result is an increase, negative result is a decrease.

To increase a value by p%, multiply by (1 + p ÷ 100). To decrease by p%, multiply by (1 − p ÷ 100). Example: increase 200 by 10% = 200 × 1.10 = 220.

If a value after a p% increase is known, the original value = after ÷ (1 + p ÷ 100). For a decrease, original = after ÷ (1 − p ÷ 100).

This calculator returns numeric results to the exact number of decimal places you choose so that exports, reports and spreadsheets match precisely.