Percentage Calculator

This Percentage Calculator answers the six percentage questions people search for most, all on one page and all live: what is X% of Y, X is what percent of Y, the percentage increase or decrease between two numbers, the reverse percentage (X is Y% of what), adding or subtracting a percentage, and the difference between percentage points and percent. There is no Calculate button to press — type a number and the answer appears instantly, together with the exact formula used, so you can check the working or copy it into a spreadsheet.

A percentage is simply a fraction of 100. "Percent" means "per hundred", so 15% is 15 ÷ 100 = 0.15. To find 15% of 80, multiply: 0.15 × 80 = 12. To find what percent 30 is of 120, divide the part by the whole and multiply by 100: 30 ÷ 120 × 100 = 25%. To reverse a percentage — say you know 45 is 15% of some number — divide by the percentage as a decimal: 45 ÷ 0.15 = 300. Those three rearrangements of part = percent × whole cover almost every everyday percentage problem, from tips and test scores to commission and tax.

Percentage change compares a new value with an old one: (new − old) ÷ old × 100. A price that rises from 50 to 65 has increased by (65 − 50) ÷ 50 × 100 = 30%, while a figure that falls from 80 to 60 has decreased by 25%. The starting value always goes on the bottom, which is why percentage changes are not symmetrical: a 50% rise followed by a 50% fall does not bring you back to where you started. 100 rises to 150, then falls by half to 75 — a net 25% loss. The same trap catches people with salary cuts, stock prices and stacked discounts.

Adding or subtracting a percentage is the shortcut shops, accountants and payroll teams use every day. Adding 20% to 150 gives 150 × 1.20 = 180; subtracting 20% gives 150 × 0.80 = 120. Multiplying by (1 + rate) or (1 − rate) is faster and less error-prone than working out the percentage and then adding it on. It is how VAT and sales tax are added to a net price, how a markup is applied to cost, and how a sale discount is taken off a price tag.

Percentage points and percent are not the same thing, and mixing them up is one of the most common mistakes in news reports and financial documents. If a loan rate moves from 4% to 5%, it has risen by 1 percentage point, but the rate itself is 25% higher because (5 − 4) ÷ 4 × 100 = 25. Use percentage points when you compare two rates that are already percentages — interest rates, tax rates, unemployment, conversion rates, election shares — and use percent when you describe how much one of them has grown relative to its starting level.