Percentage calculator — discounts, tips and % change
To calculate a percentage, divide the part by the whole and multiply by 100 — so 30 out of 200 is 15%. To take a percentage of a number, multiply by the percent and divide by 100 — 15% of 200 is 30. The free percentage calculator does both instantly, right in your browser.
This guide walks through the everyday jobs behind those formulas: sale prices and savings with the discount calculator, tips and bill splitting with the tip calculator, and percentage change for prices, salaries and grades — each with a worked example you can follow with your own numbers.
The three percentage modes: % of, is what % and % change
Almost every percentage question you meet is one of three modes, and the percentage calculator has a switch for each. Pick the mode, type two numbers, and the answer updates as you type — no equals button, no rounding surprises.
- % of a number — what is 15% of 200? Multiply 200 by 15, divide by 100: the answer is 30.
- Is what % — 30 is what percent of 200? Divide 30 by 200, multiply by 100: 15%.
- % change — a price moved from 80 to 100. Take the difference, divide by the old value, multiply by 100: (100 − 80) ÷ 80 × 100 = +25%.
How to take 20% off a price
The fastest mental shortcut: a 20% discount means you pay 80% of the price, so multiply by 0.8. A 250 price tag with 20% off becomes 250 × 0.8 = 200, and you save 50. The discount calculator shows both numbers — sale price and amount saved — at the same time, which is exactly what you want mid-shopping. Here is the whole flow:
- Open the discount calculator and enter the original price — say 250.
- Enter the discount percent — 20 — or nudge it to compare offers.
- Read both results instantly: the sale price (200) and how much you save (50).
- Change either number and the result recalculates live — try 25% to see the price drop to 187.50.
What was the original price? Reverse discount math
You paid 340 for something marked 15% off — what did it cost before the sale? Divide what you paid by (1 − the discount as a decimal): 340 ÷ 0.85 = 400. The common mistake is adding 15% back onto 340, which gives 391 — wrong, because the discount was taken from the larger original price, not from the amount you paid.
To sanity-check any receipt, flip the numbers into the percentage calculator in "is what %" mode: your 60 saving on a 400 original is 60 ÷ 400 × 100 = exactly 15%. If the store advertised 20% and your check says 15%, now you know before you leave the till.
How much to tip and how to split the bill
How much you tip depends on where you are: in the US, 15–20% of the pre-tax bill is standard (18% is a safe middle); in Egypt, around 10% is common, often on top of a service charge already on the check; in much of Europe, service is included and rounding up is enough. On a 100 bill at 18%, the tip is 18 and the total is 118.
Splitting is where the tip calculator earns its place: enter the bill, pick the tip percent, set the number of people, and it shows the per-person share — 118 split four ways is 29.50 each. It runs entirely in your browser, so it works at the table on your phone. Eating out abroad? Check the currency converter first — its rates come from live sources, and the currency converter guide explains how those rates work.
Percentage change, salary raises and grade percentages
Percentage change has one formula: (new − old) ÷ old × 100. A salary that moves from 6,000 to 6,900 changed by (6,900 − 6,000) ÷ 6,000 × 100 = +15%. A price that drops from 100 to 80 changed by −20% — the sign tells you the direction, the number tells you the size. The percentage calculator's % change mode does this in one step, in either direction.
Grades are the same math in "is what %" clothing: 342 marks out of 400 is 342 ÷ 400 × 100 = 85.5%. And when a problem chains several operations — averaging three exam percentages, say — the free calculator handles the longer arithmetic without leaving the site.
Free, private and always in your pocket
All three tools — percentage, discount and tip — are free with no sign-up, no daily caps and no ads maze between you and the answer. They calculate entirely on your device: the prices, bills and grades you type are never uploaded anywhere, and once the page has loaded they keep working even when the connection drops. Native Carbide apps for Android and iOS are coming soon with the same tools built in.
The sibling calculators are one tap away when the question changes shape: the unit converter for cm-to-inches and kg-to-lbs (the cheat sheet lists the common pairs), and the age calculator for exact ages and date gaps — covered step by step in the age and date guide.
Frequently asked questions
What is 15% of 200?
30. Multiply 200 by 15 and divide by 100 — or move the decimal: 10% of 200 is 20, half of that is 10, together 30. The percentage calculator gives the same answer as you type.
Do stacked discounts add up — is 20% plus an extra 10% the same as 30% off?
No. The second discount applies to the already-reduced price: 100 with 20% off is 80, then 10% off 80 is 72 — a 28% total discount, not 30%. Run each step through the discount calculator to see the real final price.
How do I split a bill so everyone pays a round amount?
Set the people count in the tip calculator and nudge the tip percent up until the per-person share lands on a round number — moving an 18% tip to 19–20% usually gets there, and the difference goes to the server.
Are the numbers I enter uploaded anywhere?
No. The percentage, discount and tip calculators run entirely in your browser — your prices, bills and grades are processed on your own device and never sent to a server.
Is the percentage calculator free? Is there a usage limit?
Yes, completely free — no sign-up, no trial, no daily limit. All three calculators work on any modern browser, on desktop or phone.
Percentages stop being fiddly once each job has its own tool: the percentage calculator for % of, is-what-% and change, the discount calculator for sale prices and savings, and the tip calculator for the bill at the table. Keep the formulas from this guide for mental math — and the tools for everything else.