Percent of, change, reverse, tip, and discount calculations. Free, private, runs in your browser.
100% private — your files never leave your browser. All processing happens locally on your device.
Result
30
20% × 150 = 30
The percentage calculator ships six modes covering every common percent-related question. `X% of Y` finds a fraction of a known value — discounts, tax amounts, tip portions, probabilities. `X is what % of Y` goes the other way — you scored 42 out of 50, what's your grade? `% change` measures growth or shrinkage between two values — last month's revenue vs this month's. `Reverse percentage` recovers the original value from a final value and the change that produced it — useful for backing out tax, markup, or commissions. `Tip` bundles the common restaurant math with a per-person split. `Discount` shows what you save and what you pay at the till.
A 50% increase followed by a 50% decrease does not return you to the original value. Start at 100, add 50% → 150, subtract 50% → 75. You've ended up 25% lower. This is why reverse percentage exists as its own mode: when you know a value is already reduced by X% and want to know what it started as, simple subtraction gives the wrong answer. The correct move is to divide by (1 + X/100) if the change was positive, or by (1 − X/100) if negative. The tool does this for you, but it's worth understanding before you eyeball percent math in your head.
Typical US restaurant tips are 18-22% of the pre-tax bill; higher for exceptional service, lower in casual settings. Some countries include service in the bill (look for 'service compris' on French receipts) and leaving an extra tip is optional or unusual. The tool doesn't care about local norms — enter whatever tip percentage fits the context. The per-person split assumes even division; for weighted splits by what each person ordered, run the tip calc on the subtotal and divide separately.
Discount mode answers two questions at once: the final price the customer pays and how much they save. Sellers use the same formula in reverse — if a product sold 20% off for $80, the original price was $100 and the markdown was $20. For compound discounts (20% off, plus an extra 10% at checkout), apply them sequentially — 20% off $100 is $80, then 10% off $80 is $72 (not $70). The tool handles one discount at a time; apply twice for stacked offers.
All calculations happen on your device. No numbers are transmitted anywhere. Privacy matters even for arithmetic — salary calculations, invoice amounts, and personal finance inputs shouldn't need to leave your browser just to answer a basic percent question.
Given a final value and the percentage change, reverse percentage gives you the original value. Example: a price with tax of $120 at 20% tax gives an original price of $100. Useful for backing out tax, commission, or any percentage applied on top.
Yes. Enter the bill, tip percent, and number of people — the tool returns the tip amount, the total, and the amount each person owes.
No, and this catches people out. 100 + 50% = 150. 150 − 50% = 75, not 100. A 50% increase followed by a 50% decrease nets out to a 25% decrease. Use the reverse-percentage mode to back out a specific change correctly.