Five ways to calculate percentages — find X% of a number, percentage change, increase or decrease by %, and more. Instant results, no sign-up.
What is X% of Y?
Quick Reference
Every percentage calculation you'll ever need — no formula memorisation, no mental arithmetic.
Results appear as you type — no submit button, no waiting. Switch between all five calculation modes with a single click.
Every result includes the formula used, so you can see exactly how the answer was calculated and learn the method for future reference.
Increases show in green, decreases in red — at a glance you know whether a change is positive or negative, no need to read the sign.
All calculations happen in your browser. Nothing is sent to a server — your numbers stay on your device.
Fully responsive — use it on desktop, tablet, or phone. The layout adapts to any screen size with large, easy-to-tap inputs.
A formula cheat sheet is built into the tool — all five percentage formulas in one place so you can double-check your calculations any time.
Percentages appear in almost every area of daily life — here are the most common real-world scenarios.
Work out the sale price when something is 20% or 30% off, and see how much you actually save in dollar terms.
Calculate portfolio gains and losses, interest comparisons, and the percentage return on any investment.
Track revenue growth month-on-month, calculate profit margins, measure KPI completion, and work out commission.
Convert test scores to percentages, calculate grade averages, or find out what you need on the final exam to pass.
Work out a 15% or 20% tip at a restaurant, or split costs proportionally in a group.
Track body weight change as a percentage, calculate macronutrient ratios, or measure progress toward a fitness goal.
Calculate property price changes, rental yield as a percentage, stamp duty portions, or mortgage interest breakdowns.
Calculate a percentage raise, compare pay increases between offers, or work out how much tax is taken as a percentage of gross pay.
20% of 150 = (20 ÷ 100) × 150 = 30. Use the “X% of Y” mode and enter 20 and 150 to get the answer instantly. This is the most common percentage calculation — used for discounts, tips, and tax.
Percentage change = ((New Value − Old Value) ÷ |Old Value|) × 100. A positive result is an increase; negative is a decrease. Use the “Percentage Change” tab — just enter the old and new values and the result appears automatically, colour-coded green or red.
They use the same formula. “Percentage change” is the general term that can be positive (an increase) or negative (a decrease). “Percentage increase” specifically refers to a positive change. Our calculator labels the result as either an increase or decrease automatically.
30 ÷ 120 × 100 = 25%. Use the “X is what % of Y” mode and enter 30 and 120. This calculation is useful for test scores, market share analysis, and measuring progress toward a target.
If you know the discounted price and the percentage off, divide the discounted price by (1 − discount/100). For example, if $80 is the price after a 20% discount: $80 ÷ 0.80 = $100 original price. This is called a reverse percentage calculation.
Use the “Increase by %” mode — enter your current salary and the percentage raise. For example, a $60,000 salary with a 5% raise becomes $60,000 × 1.05 = $63,000. The tool also shows the exact dollar amount added.
15% of 200 = (15 ÷ 100) × 200 = 30. A quick mental shortcut: 10% of 200 is 20, and 5% is half of that (10), so 15% = 20 + 10 = 30. Use the tool for larger numbers where mental arithmetic gets harder.
Yes — the tool is fully responsive and works on iOS and Android browsers. Tap the mode button at the top to switch between calculation types, and all inputs are optimised for touchscreen keyboards.
No — this is a common misconception. If $100 increases by 50% to $150, then decreases by 50%, you get $75, not $100. Each percentage is applied to a different base value. Use the percentage change tool to verify: from $150 to $75 is exactly −50%.
A percentage is a way of expressing a number as a fraction of 100. The word “percent” comes from the Latin per centum, meaning “by the hundred.” When we say 45%, we mean 45 out of every 100, or 45/100 = 0.45 as a decimal. Percentages are the universal language of comparison — used everywhere from bank statements to school reports to nutritional labels.
1. What is X% of Y? This is the most common percentage question. To find 25% of 80: divide 25 by 100 to get 0.25, then multiply by 80 to get 20. Used for discounts (“30% off $120”), tax (“GST of 10% on $500”), tips (“15% tip on $60”), and interest calculations.
2. X is what % of Y? Divide X by Y then multiply by 100. Used for test scores (“42 out of 50 = 84%”), market share (“our revenue is what % of the total market?”), and tracking completion (“I've read 80 of 320 pages — what % done am I?”).
3. Percentage change from X to Y. Formula: ((New − Old) ÷ |Old|) × 100. Used in finance for portfolio returns, in business for month-on-month revenue comparisons, and in science for measuring experimental change. A positive result is an increase; negative is a decrease.
4. Increase a number by X%. Multiply the number by (1 + X/100). A 15% raise on a $50,000 salary: $50,000 × 1.15 = $57,500. Used for salary negotiations, price increases, markup calculations, and compound growth projections.
5. Decrease a number by X%. Multiply by (1 − X/100). A 20% discount on $250: $250 × 0.80 = $200. Used for discounts, depreciation, budget cuts, and anything that reduces by a stated percentage.
You can often estimate percentages quickly without a calculator. 10% of any number: move the decimal point one place left (10% of 340 = 34). 5% is half of 10% (5% of 340 = 17). 1% is the number divided by 100. 15% is 10% + 5%. 20% is 10% doubled. 25% is the number divided by 4. 50% is the number divided by 2.
These shortcuts are especially useful for mental maths at restaurants, shops, and anywhere you need a quick estimate. For precise figures — especially with decimals, large numbers, or multiple steps — use the calculator above.
These terms sound similar but mean very different things. If an interest rate rises from 4% to 6%, it has increased by 2 percentage points — but the percentage change is ((6 − 4) ÷ 4) × 100 = 50%. Politicians and journalists often confuse these deliberately or by accident. Always clarify which is meant: “the rate went up 2 percentage points” is factual, while “the rate went up 50%” sounds more dramatic but is equally accurate.
A 25% increase followed by a 25% decrease does not return you to the original value. If you start with $100 and increase by 25% you get $125. Decrease $125 by 25% and you get $93.75 — not $100. This is because each percentage operates on a different base. This asymmetry matters in investing (a 50% loss requires a 100% gain to recover), in pricing strategy, and in interpreting any sequence of percentage changes.