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
Is the percentage calculator free to use?
Yes. It’s free and runs in your browser - no signup, no install.
How do I find X% of a number?
Pick the ‘What is X% of Y’ mode, type the percentage and the number, and read the result. For example, 18% of 2500 = 450.
How do I calculate percent increase or decrease?
Use the change mode. Enter the old and new values - the tool returns the percent change: (new − old) / old × 100.
Can I add tax or GST using percentages?
Yes. Use the ‘X% change from Y’ mode to increase a base amount by a percentage - ideal for adding tax, service charges, or markups.
Are there rounding issues?
Only round the final value. Rounding mid-calculation introduces small errors. The tool keeps full precision internally and displays the rounded result.
Does the tool store my numbers?
No. Calculations run in your browser and aren’t stored on our servers.
User reviews
No reviews yet. If you used the tool, you can share feedback on our feedback page.
Ready to crunch percentages?
Pick a mode, type the numbers, and read the answer live.