Percentage Calculator

Work out any percentage in one step. Switch between three modes: a percent of a number, the percentage change from one value to another, and what percent one number is of another.

Result30

How this calculation works

"X% of a number" multiplies the base by the percentage divided by 100. So 15% of 200 is 200 × 15 ÷ 100 = 30.

"Percentage change" measures how much a value grew or shrank relative to the starting value: (new − old) ÷ |old| × 100. A drop gives a negative result.

"What percent is A of B" divides the part by the whole and multiplies by 100: A ÷ B × 100.

Worked example

A jacket's price rises from 200 to 250. The change is (250 − 200) ÷ 200 × 100 = 25%. If instead you want 25% of 200, that is 200 × 25 ÷ 100 = 50.

Three ways to work with percentages

A percentage is simply a number out of one hundred — the word comes from the Latin "per centum". Almost every real-world percentage question is one of three types, which is why this calculator has three modes.

Finding a percentage of a number answers "what is 15% of 80?" and is used for tips, taxes, commissions and discounts. Percentage change answers "how much did this grow or shrink?" and is used for price moves, growth rates and returns. The ratio mode answers "A is what percent of B?" and is used for test scores, market share and completion rates.

Percentage vs. percentage points

This is the most common percentage mistake. If an interest rate rises from 4% to 6%, that is a 2 percentage-point increase, but a 50% relative increase (2 ÷ 4). News headlines frequently confuse the two.

Rule of thumb: use "percentage points" when subtracting two percentages, and "percent" when describing how much one value changed relative to another.

Reverse percentage: finding the original

If a jacket costs 80 after a 20% discount, the original price was not 80 × 1.2. Because the 20% was taken off the original, you divide: 80 ÷ (1 − 0.20) = 100. The same logic removes tax from a gross amount: net = gross ÷ (1 + tax rate).

Common percentages as fractions

Recognising these makes mental math fast:

Percentage	Fraction	Quick tip
10%	1/10	Move the decimal one place left
12.5%	1/8	Half of 25%
20%	1/5	Divide by 5
25%	1/4	Divide by 4
33.3%	1/3	Divide by 3
50%	1/2	Halve it
75%	3/4	Three quarters

Frequently asked questions

How do I calculate a percentage of a number?

Multiply the number by the percentage and divide by 100. For 20% of 150: 150 × 20 ÷ 100 = 30. Use the "percent of a number" mode above.

What is the difference between percentage change and percentage points?

Percentage change is relative to the starting value. Percentage points are a simple subtraction of two percentages. Going from 10% to 15% is a 5 percentage-point rise but a 50% relative increase.

Is my data sent anywhere?

No. Every calculation runs entirely in your browser. Nothing you type is uploaded or stored.

How do I find the original price before a discount?

Divide the discounted price by (1 minus the discount as a decimal). If an item is 80 after 20% off: 80 ÷ 0.80 = 100. This "reverse percentage" undoes the discount.

How do I add or remove sales tax?

To add tax, multiply by (1 + tax rate): 100 × 1.08 = 108 for 8% tax. To remove tax from a gross price, divide: 108 ÷ 1.08 = 100.

What is a percentage of a percentage?

Multiply the two decimals. 50% of 20% is 0.50 × 0.20 = 0.10 = 10%. This comes up when discounts or probabilities are chained.

What is percentage error?

Percentage error = |measured − true| ÷ |true| × 100. It expresses how far an estimate is from the correct value, relative to that value.

This tool is provided for general information only. Verify important figures independently. · Last reviewed: August 25, 2026