Percentage Calculator
A fast online percentage calculator — find X% of Y, what % one number is of another, and percent increase or decrease. Runs in your browser, no signup.
Use this percentage calculator for everyday maths: how much is 18% of 2500, percent discount on a price, percent marks on a test, or percent change from last month. Pick the mode and type — results update live.
Supports increases and decreases, add / subtract percentages for tax and markup, and decimal-precision control for financial work. Handy for shopping, school, finance, and quick sanity checks.
How to calculate a percentage
Three steps and you have your answer.
1. Pick a mode
X% of Y, X is what % of Y, or percent change.
2. Enter values
Type the numbers — decimals and negatives allowed.
3. Read & copy
Result updates live. Copy with one click.
Percentage modes with formulas
The exact question each mode answers.
| Mode | Example | Formula |
|---|---|---|
| What is X% of Y? | 15% of 200 = 30 | X / 100 × Y |
| X is what % of Y? | 45 of 200 = 22.5% | X / Y × 100 |
| Percent increase / decrease | From 200 → 250 = +25% | (New − Old) / Old × 100 |
| X% change from Y | 200 up by 15% = 230 | Y × (1 + X / 100) |
Common everyday uses
Discounts & deals
Find the saved amount and final price from a % off.
Tax & tips
Add GST / VAT / service charge to a base amount.
Grades & scores
Work out marks as a percentage of total.
Finance & growth
Simple percent increases or decreases over time.
Common pitfalls
Confusing ‘of’ with ‘off’
20% of 100 = 20; 20% off 100 = 80. Pick the right mode before you trust the result.
Applying multiple percentages
Two 10% discounts aren’t 20% off. They’re 19% (0.9 × 0.9). Combine carefully.
Rounding mid-calculation
Round only the final value. Rounding each step inflates small errors.
Negative percent change pitfalls
A 50% drop needs a 100% rise to recover. Percent changes aren’t symmetric.
What this tool supports
| Feature | Supported | Notes |
|---|---|---|
| ‘What is X% of Y’ | Yes | Classic percent calculation. |
| ‘X is what % of Y’ | Yes | Inverse — find the percentage. |
| Percent increase / decrease | Yes | Compare old vs new value. |
| Add / subtract a percentage | Yes | Markups, discounts, tax. |
| Decimal precision control | Yes | Round to the digits you need. |
| Instant live results | Yes | Output updates as you type. |
| Account required | No | No signup, no install. |
Frequently Asked Questions
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Ready to crunch percentages?
Pick a mode, type the numbers, and read the answer live.