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Percentage Calculator

Work out 'P% of X', 'A is what % of B', percent change, and increase/decrease by a percentage — all on one page.

What is% of?
Result
30
20%

X × P ÷ 100: 150 × 20 ÷ 100 = 30

Formulas

P% of X = X × P ÷ 100
A is what % of B = A ÷ B × 100
change F→T = (T − F) ÷ |F| × 100
X ± P% = X × (1 ± P ÷ 100)

P is the percentage, X the number, A the part, B the whole, F the start value, and T the end value.
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What is a Percentage Calculator?

A percentage calculator turns everyday 'percent' questions into instant answers. Percent simply means 'per hundred', so 25% is 25 out of every 100, or the fraction 0.25. This tool covers the four questions that come up most often: what is P% of a number, what percentage one number is of another, how much something changed in percentage terms, and what a value becomes after a percentage increase or decrease. Percentages appear everywhere — discounts and sales tax, tips, interest rates, exam scores, statistics in the news, and growth figures at work. Getting them right saves money and avoids embarrassing mistakes. Each mode here shows the formula and a visual so you can see, not just compute, the result.

How to Use

1. Pick a mode: '% of a number', 'What %', '% change', 'Increase %', or 'Decrease %'. 2. Fill in the two numbers in the sentence. 3. The result, formula, and chart update instantly. Switch modes to answer a different question with the same numbers.

Formulas & Definitions

P% of X = X × P ÷ 100. For example 20% of 150 = 150 × 20 ÷ 100 = 30. A is what % of B = A ÷ B × 100. For example 30 is 30 ÷ 150 × 100 = 20% of 150. Percent change from F to T = (T − F) ÷ |F| × 100. From 100 to 150 is +50%. Increase X by P% = X × (1 + P ÷ 100); decrease = X × (1 − P ÷ 100). 80 increased by 25% = 100.

Interpreting Results

A positive percent change means growth, a negative one a decline. Be careful with the direction: going from 100 to 150 is a 50% increase, but going back from 150 to 100 is only a 33% decrease — the base changes, so the percentages are not symmetric. Also distinguish 'percent' from 'percentage points': if an interest rate rises from 4% to 6%, that is a 2 percentage-point rise but a 50% increase. When chaining discounts, multiply rather than add: 30% off then 10% off is about 37% off, not 40%.

Frequently Asked Questions

What does percent actually mean? ▾

Percent means 'per hundred'. So 40% is 40 out of every 100, equal to the fraction 40/100 = 0.4. To find P% of a number, multiply the number by P and divide by 100.

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

Divide the part by the whole and multiply by 100: A ÷ B × 100. For example, 30 out of 150 is 30 ÷ 150 × 100 = 20%.

What is the difference between a percentage increase and decrease? ▾

An increase adds to the base (X × (1 + P/100)); a decrease subtracts from it (X × (1 − P/100)). They are not reversible: a 50% increase followed by a 50% decrease does not return you to the start.

What is the difference between percent and percentage points? ▾

A percentage point is the arithmetic gap between two percentages. Rising from 20% to 25% is a 5 percentage-point change but a 25% relative increase. Confusing the two is a common reporting error.

How do I calculate a discount or sales tax? ▾

For a discount, decrease the price by the discount percentage (use 'Decrease %'). For tax, increase the price by the tax rate (use 'Increase %'). For dedicated tools, see our discount and sales-tax calculators.