Quick answers to the most common questions about percentage math and using this site.
Multiply the number by the percentage and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12. Or convert the percentage to a decimal (15% → 0.15) and multiply: 80 × 0.15 = 12.
(new − old) ÷ old × 100. A value going from 50 to 75 is (75 − 50) ÷ 50 × 100 = 50% increase. To apply an increase, multiply by (1 + percent/100).
Percent is a relative measure; percentage points is the absolute difference between two percentages. A poll going from 40% to 44% is a 4 percentage point increase but a 10% relative increase.
Divide the part by the whole and multiply by 100. 12 of 80 is 12 ÷ 80 × 100 = 15%.
Markup is profit as a percentage of cost; margin is profit as a percentage of sell price. A 50% markup yields a 33.3% margin on the same dollar profit.
Because each discount is applied to the already-reduced price. 20% off then 10% off is 28% off total, not 30%. The math: 0.80 × 0.90 = 0.72, so total discount = 28%.
Yes, in many contexts. Growth rates can exceed 100% (a value that triples grew by 200%). Markup can be any positive number. But discounts and shares of a fixed whole cannot exceed 100%.
Yes, completely free with no sign-up. The site is supported by display advertising; your calculation inputs and results never leave your browser.
After the first load, yes. All calculation logic runs in your browser. You can disconnect from the internet and the page continues to work until you close the tab.
Yes — an embed snippet is provided on the homepage. Copy the <iframe> code and paste it into your HTML. The calculator will render in your page with full functionality.
All calculations use double-precision floating-point arithmetic, which is accurate to about 15 significant digits. Results are rounded to 4 decimal places for display, with trailing zeros trimmed.
All modern browsers from the last 5 years: Chrome, Firefox, Safari, Edge. The calculator does not work in Internet Explorer.