What this tool does

The Percentage Calculator covers the three questions people ask most often. Each one has its own pair of boxes and its own button, so you can use whichever fits your problem.

The three calculators

1. What is X% of Y? Enter the percentage and the number. Example: 20% of 150 is 30.
2. X is what % of Y? Enter two numbers. Example: 30 is 15% of 200.
3. Percentage change from X to Y. Enter the starting and ending values. Example: going from 80 to 100 is a 25% increase.

The formulas

• X% of Y = (X ÷ 100) × Y
• X is what % of Y = (X ÷ Y) × 100
• Percentage change = ((new − old) ÷ |old|) × 100

Tips for better results

• A percentage change and a percentage point change are different. Going from 10% to 12% is a rise of 2 percentage points but a 20% increase.
• Two discounts do not add up: 20% off followed by another 10% off is 28% off in total, not 30%.
• To work out a price before a discount, divide the sale price by (1 − the discount rate).

Privacy: what happens to your data

This tool runs in your browser, so the content you enter stays on your device and is not sent to Tantool's servers. See the Privacy Policy for the full picture.

Limitations to know about

• "What percent of 0" and "change from 0" are not defined, so the tool asks you to enter a different value.
• Results are shown to a few decimal places, so very long decimals are rounded.
• There is no chaining of several steps; run each calculation separately.

Frequently asked questions