Age Calculator
Calculate your exact age in years, months and days — plus total weeks, days, hours, minutes and seconds.
Calculator Tools
Open Tool
Percentage Calculator
Work out percentages, "what percent" values, percentage increase or decrease, and percentage difference — instantly.
Runs entirely in your browser — nothing you type is uploaded.
How to use the Percentage Calculator
- Choose the type of calculation: X% of Y, X is what % of Y, Increase / Decrease, or Difference.
- Enter your two numbers in the fields — the labels change to match the calculation you picked.
- Press Calculate (or the Enter key). The answer appears instantly, with a plain-language explanation you can copy.
- Use Reset to clear the fields and start again.
What is a percentage calculator?
A percentage calculator is a free tool that does the arithmetic behind percentages for you, so you do not have to remember the formulas or reach for a calculator app. It covers the four questions people ask most: how much a percentage of a number is, what percentage one number is of another, how much a value has grown or shrunk, and how far apart two values are in percentage terms.
How to calculate percentages
A percentage is simply a fraction out of 100. To find a percentage of a number, convert the percentage to a decimal (divide by 100) and multiply. To find what percentage one number is of another, divide the part by the whole and multiply by 100. Percentage change compares a new value to an original one, while percentage difference compares two values evenly, without treating either as the starting point.
Common percentage formulas
- X% of Y —
(X ÷ 100) × Y. Example: 20% of 150 =0.20 × 150 = 30. - X is what percent of Y —
(X ÷ Y) × 100. Example: 30 is what percent of 150?30 ÷ 150 × 100 = 20%. - Percentage increase / decrease —
((New − Old) ÷ Old) × 100. Example: 100 → 120 =20% increase; 120 → 100 =16.67% decrease. - Percentage difference —
|A − B| ÷ ((A + B) ÷ 2) × 100. Example: between 100 and 120 =18.18%.
Worked examples
A shirt costs 40 and is 25% off: 25% of 40 = 10, so you save 10. A score rose from 80 to 100: that is a (100 − 80) ÷ 80 × 100 = 25% increase. Two teams scored 45 and 55 points: the percentage difference is |45 − 55| ÷ 50 × 100 = 20%. Everything runs in your browser, so the maths is instant and private.
Is it private?
Yes. The Percentage Calculator does all of its work locally in your web browser using JavaScript. The numbers you enter are never sent to a server, never stored, and never shared. There is no sign-up and no tracking.
Frequently Asked Questions
Is the Percentage Calculator free?
Yes. It is completely free to use, with no account, sign-up or limits.
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 is what percent of 150? 30 ÷ 150 × 100 = 20%. Use the “X is what percent of Y?” mode to do it automatically.
What is the difference between percentage change and percentage difference?
Percentage change measures how much a value went up or down from an original value: (new − old) ÷ old × 100. Percentage difference compares two values without treating either as the “original”: |A − B| ÷ ((A + B) ÷ 2) × 100.
Is my data sent anywhere?
No. All calculations run locally in your browser using JavaScript — nothing you type is uploaded or stored.
Does it handle decimals and negative numbers?
Yes. You can enter decimals and negative numbers, and the calculator handles the maths correctly, showing a clear error only when a calculation is mathematically undefined (such as dividing by zero).