A percentage is a number expressed as a fraction of 100. The word comes from the Latin per centum, meaning "by the hundred." When you see 25%, it means 25 out of every 100 — or one quarter. Percentages are one of the most practical tools in everyday arithmetic, used for everything from calculating a restaurant tip to understanding a salary raise.
The three core percentage formulas
Every percentage calculation comes back to one of three formulas. To find X% of a number: multiply the number by X and divide by 100. To find what percentage A is of B: divide A by B and multiply by 100. To find percentage change between two values: subtract the original from the new, divide by the original, and multiply by 100.
Percentage vs percentage points
These are easy to confuse. If an interest rate rises from 2% to 3%, that is a 1 percentage point increase — but a 50% relative increase. Percentage points measure absolute differences between two percentages. The relative percentage change measures how large that shift is relative to where you started.
Real-world percentage examples
Shopping discounts
To find the sale price after a discount, multiply the original price by (1 − discount/100). A $120 jacket with 30% off: $120 × 0.70 = $84. The saving is $36. This is exactly what our discount calculator does instantly.
Restaurant tips
A quick mental trick: to find 20%, divide the bill by 10 (to get 10%), then double it. For 15%, find 10% and add half again. For precise splits across multiple people, use the tip calculator above — it handles any tip percentage and any number of diners.
Salary and pay rises
A 5% raise on a $55,000 salary: $55,000 × 0.05 = $2,750 raise, making the new salary $57,750. Use the percentage change calculator to verify any quoted raise percentage, or to calculate what raise percentage you'd need to reach a target salary.
Business markup vs margin
Markup and margin are often confused. Markup is the percentage added to the cost price. Margin is the profit as a percentage of the selling price. A 50% markup on a $40 item gives a $60 selling price, but the margin on that sale is only 33.3% ($20 profit ÷ $60 selling price). The markup calculator above shows both figures simultaneously.
Frequently asked questions
Multiply the number by the percentage and divide by 100. For example, to find 20% of 150: (20 × 150) ÷ 100 = 30. Or enter the values in the "% of Number" calculator above for an instant result.
Use the formula: ((New − Old) ÷ Old) × 100. If a price goes from $80 to $100, the change is ((100 − 80) ÷ 80) × 100 = 25% increase. A negative result means a decrease.
Multiply the original price by (1 − discount% ÷ 100). A 20% discount on $80: $80 × 0.80 = $64. The saving is $80 − $64 = $16. The discount calculator above shows the final price and saving together.
Multiply the bill by the tip percentage divided by 100. A 20% tip on $60: $60 × 0.20 = $12 tip, total bill $72. To split equally, divide the total by the number of people. Standard tips are 15–20% in the US, 10–15% in the UK.
Markup is the profit as a percentage of the cost price. Margin is the profit as a percentage of the selling price. A 50% markup on a $40 item = $60 selling price. The margin is $20 ÷ $60 = 33.3%. Same profit, different percentage — which is why the two numbers are never equal (except at 0%).
Divide your score by the total possible points and multiply by 100. Score of 42 out of 50: (42 ÷ 50) × 100 = 84%. The grade calculator above also shows the corresponding letter grade.
To add VAT to a price: Price × (1 + VAT% ÷ 100). To add 20% VAT to $100: $100 × 1.20 = $120. To remove VAT from a price that already includes it: Price ÷ (1 + VAT% ÷ 100). So $120 ÷ 1.20 = $100 before VAT.
Yes — all eight calculators are completely free with no signup, no ads, and no limits. All calculations happen instantly in your browser and nothing is sent to any server.
To add tax to a price: Total = Price × (1 + Rate ÷ 100). A $100 item with 8.5% tax: $100 × 1.085 = $108.50. To remove tax from a price that already includes it (reverse calculation): Pre-tax = Total ÷ (1 + Rate ÷ 100). So $108.50 ÷ 1.085 = $100 before tax.
"20% off" means the price is reduced by one fifth. On a $50 item: $50 × 0.20 = $10 saving, so you pay $40. To find what percentage off an item has been reduced, use the Percent Off calculator above — enter the original and sale price and it calculates the discount percentage automatically.
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