📊 % Percentage Calculator ☆

Overview

Our Free Percentage Calculator is a free online math utility that performs all your percentage calculations instantly in your browser. Find what percentage one number is of another, take a percentage of a value, measure increase or decrease between two numbers, work out discounts and sale prices, a restaurant tip, business markups and margins, or plain ratios and proportions, all with precision. Simply enter your numbers, choose the calculation type, and the result appears immediately. The tool shows the step-by-step breakdown so you can understand exactly how the percentage was derived. All calculations happen entirely in your browser using JavaScript. Your numbers never leave your device. Perfect for students doing math homework, shoppers calculating discounts, business owners figuring margins, or anyone who regularly works with percentages. No downloads, no sign-up, no data collection.

The percentage formulas behind each mode

Each calculation type maps to a simple formula. "What is X% of Y" multiplies Y by X/100. "X is what percent of Y" divides X by Y and multiplies by 100. Percentage change compares the difference against the starting value: (new − old) / old × 100, positive for an increase and negative for a decrease. Discount price subtracts the percentage from the original, and margin divides profit by revenue. The step-by-step breakdown shows the substituted numbers, so you can verify the result and reuse the formula by hand.

Capabilities and constraints

Property	Percentage calculator behavior
Modes	Percent of value, what percent, increase/decrease, discount, margin, ratio
Precision	Full floating-point math, rounded for display
Explanation	Step-by-step breakdown with the substituted values
Inputs	Plain numbers, decimals and negatives
Processing	100% client-side JavaScript, nothing transmitted
Cost	Free, no account, no ads

Privacy: your numbers are nobody's business

Prices, salaries and business margins are sensitive. All math runs locally, nothing is stored or logged, and the page works offline after loading. No sign-up and no analytics events tied to the numbers you type.

Avoiding common percentage mistakes

• A 20% discount followed by a 20% increase does not return the original price.
• Percentage points and percent are different: 5% to 7% is a 2-point rise, a 40% increase.
• Percent change always divides by the starting value, not the final one.
• Margins are calculated on revenue; markups are calculated on cost.
• Round only at the end to avoid compounding rounding errors.

Related: browse all calculators for age, BMI, dates and unit conversions.

Percentages in practice: tax, discounts and tips

Most percentage errors come from confusing a percentage change with a percentage point. Going from 4% to 6% is a two-point rise but a 50% increase; interest rates, inflation and polling are all misread this way. Percentages also do not add when they apply in sequence: two consecutive 10% discounts leave 81% of the original price, not 80%, because the second discount applies to the reduced amount. The same logic makes a 20% rise followed by a 20% fall end 4% below the starting value. For sales tax or VAT, the calculator's reverse mode answers the question shops rarely display: if the final price is 120 including 20% tax, the pre-tax amount is 100 and the tax is 20, dividing by 1.2, not subtracting 20%. When splitting a bill, calculate the tip on the pre-tax total unless you intend to tip on the tax as well, and remember that a 15% tip on a 60 bill is 9, making the total 69. For pay rises, compare the new gross figure with the old one and check how tax bands change the net result, because a 10% raise rarely means 10% more in your account. Every mode on this page is client-side, so salary figures and invoice amounts never leave the device.