Percentage Calculator — % Of, Change, Difference & More
What is X% of Y?
% of = —
X is what percent of Y?
is what % of = —
Percentage change from X to Y
From to = —
Percentage difference between X and Y
Between and = —
Four essential percentage calculations in one place. Find what X% of a number is, work out what percentage one number is of another, calculate the percentage increase or decrease between two values, and compute the symmetric percentage difference — all in your browser with no server calls.
How it works
- 1 Pick a calculation type Choose from four common percentage problems: percent of a number, what percent of a whole, percentage change, or percentage difference. Each has its own pair of inputs.
- 2 Enter your numbers Type the values into the two input fields for the calculation you need. Results update instantly as you type — no button required.
- 3 Read the result The answer appears immediately below each section. For percentage change, a plus or minus sign indicates whether the value increased or decreased.
Your data stays private
All processing happens entirely in your browser. No files, text, or data are ever sent to our servers. You can disconnect from the internet and this tool will still work.
Frequently asked questions
- What is X% of Y?
- Multiply Y by X and divide by 100. For example, 15% of 200 = (15 / 100) × 200 = 30. Use the first section of the calculator to get this instantly.
- How do I calculate percentage change?
- Percentage change = ((new value − old value) / |old value|) × 100. A positive result means an increase; a negative result means a decrease. For example, going from 80 to 100 is a +25% change.
- What is the difference between percentage change and percentage difference?
- Percentage change is directional — it measures how much one specific value changed relative to a starting point. Percentage difference is symmetric — it measures how far apart two values are relative to their average, with no concept of 'before' and 'after'.
- How is percentage difference calculated?
- Percentage difference = (|A − B| / ((|A| + |B|) / 2)) × 100. It is symmetric, meaning swapping A and B gives the same result.
- X is what percent of Y?
- Divide X by Y and multiply by 100. For example, 30 is what percent of 200? (30 / 200) × 100 = 15%. Use the second section of the calculator for this.
- Is this calculator free and private?
- Yes. Everything runs in your browser — no numbers are sent to any server. There is no signup, no usage limit, and no ads inside the tool.