Percentage calculator

How a percentage is worked out

A percent is a hundredth of a whole. Every percentage calculation is therefore one division; only the quantity you are looking for changes. The calculator covers all three everyday cases and recalculates as you type.

• X % of Y: the formula is (X ÷ 100) × Y. For example 15 % of 2,500 is 375. Handy for discounts, tips and commission.
• X is what % of Y: the formula is (X ÷ Y) × 100. For example 30 out of 240 is 12.5 %. This is the share of a whole.
• Change from X to Y: the formula is ((Y − X) ÷ X) × 100. From 1,200 to 1,500 is an increase of 25 %.

You can type numbers either way, “1,234.5” or “1234.5”. Results are shown rounded to two decimal places and can be copied with one click.

Frequently asked questions

How do I work out a price after a discount?

Use the “X % of Y” mode, enter the discount and the original price. The “Value decreased by the percentage” card shows the price after the discount straight away.

Why are a percentage rise and fall not the same?

Because they are counted from a different base. When a price grows from 100 to 120, that is a 20 % increase. Going back from 120 to 100 is −16.67 %, because it relates to 120.

Does it handle percentage points?

A difference in percentage points is a plain subtraction: from 5 % to 7 % is 2 percentage points, but at the same time a 40 % increase. The calculator shows the percentage change; work out the points by subtracting.

Does the calculator round?

It computes at full precision and rounds only the displayed results to two decimal places. The copied value matches what you see.