Discounts
A 30% off sale on a £80 item. Mode 1 gives the discount, Mode 5 gives the sale price directly.
6 modes · Live formula · Instant
Percentage Calculator
Six ways to work with percentages — from the basic "X% of Y" to reverse percentages and increase/decrease calculations. Every result shows the formula, so you can verify the maths yourself.
What is X% of Y?
Quick:
Result
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Six Formulas
Every mode uses one of the standard percentage formulas below. Copy any formula into a spreadsheet and the numbers will match this calculator exactly.
1 — What is X% of Y?
Multiply the number by the percentage, then divide by 100.
Result = (X ÷ 100) × Y
Example: 20% of 500 = (20 ÷ 100) × 500 = 100.
2 — X is what % of Y?
Divide the number by the total, then multiply by 100.
Result = (X ÷ Y) × 100
Example: 15 out of 200 = (15 ÷ 200) × 100 = 7.5%.
3 — Percentage increase or decrease
Subtract the original from the new, divide by the original, then multiply by 100. A positive result is an increase; negative is a decrease.
Result = ((new − old) ÷ old) × 100
Example: from 80 to 100 = ((100 − 80) ÷ 80) × 100 = +25%.
4 — Increase a value by %
Multiply the value by (1 + percentage/100).
Result = Value × (1 + X/100)
Example: 200 increased by 15% = 200 × 1.15 = 230.
5 — Decrease a value by %
Multiply the value by (1 − percentage/100).
Result = Value × (1 − X/100)
Example: 200 decreased by 15% = 200 × 0.85 = 170.
6 — X is Y% of what number?
Divide the part by the percentage, then multiply by 100.
Result = (X ÷ Y) × 100
Example: 30 is 15% of what? (30 ÷ 15) × 100 = 200.
Common Calculations
Every answer was verified against the calculator above.
| Question | Calculation | Answer |
|---|---|---|
| What is 20% of 500? | (20 ÷ 100) × 500 | 100 |
| What is 15% of 200? | (15 ÷ 100) × 200 | 30 |
| What is 7.5% of 80? | (7.5 ÷ 100) × 80 | 6 |
| What is 125% of 40? | (125 ÷ 100) × 40 | 50 |
| 15 is what percent of 200? | (15 ÷ 200) × 100 | 7.5% |
| 45 is what percent of 60? | (45 ÷ 60) × 100 | 75% |
| From 80 to 100 — percent change? | ((100 − 80) ÷ 80) × 100 | +25% |
| From 100 to 80 — percent change? | ((80 − 100) ÷ 100) × 100 | −20% |
| 200 increased by 15%? | 200 × 1.15 | 230 |
| 200 decreased by 15%? | 200 × 0.85 | 170 |
| 30 is 15% of what? | (30 ÷ 15) × 100 | 200 |
| £80 after 20% discount — original? | 80 ÷ 0.8 | £100 |
When You'll Need This
Tips
20% tip on a £47.50 meal — Mode 1 gives the tip amount instantly.
Interest & growth
An investment grew from £1,200 to £1,500. Mode 3 tells you the return.
Test scores
42 correct out of 50. Mode 2 converts that to a percentage grade.
Tax
VAT, sales tax or income tax — any tax expressed as a percentage uses Mode 1 or Mode 4.
Price drops
From £250 down to £200 — Mode 3 shows the drop as a percentage.
Inflation
Prices rose from £4 to £5 — Mode 3 says +25%. Mode 4 tells you next year's price after any increase.
Savings targets
You saved £300 of a £1,200 goal. Mode 2 shows you're 25% of the way there.
Percentage FAQ
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. Example: 20% of 500 = (20 × 500) ÷ 100 = 100.
How do I calculate percentage increase?
Subtract the original from the new, divide by the original, then multiply by 100. Example: from 80 to 100 = ((100 − 80) ÷ 80) × 100 = 25% increase.
How do I calculate percentage decrease?
Subtract the new from the original, divide by the original, then multiply by 100. Example: from 100 to 80 = ((100 − 80) ÷ 100) × 100 = 20% decrease.
What is the difference between percentage change and percentage difference?
Percentage change divides the difference by the original value. Percentage difference divides the difference by the average of the two values. Change is used when one value is a starting point; difference is used when neither value is a baseline.
How do I work out the original price after a discount?
Divide the sale price by (1 minus the discount divided by 100). Example: sale price £80 after 20% off means the original was £80 ÷ 0.8 = £100. Use Mode 6 for this.
What is 20% of 100?
20% of 100 is 20. Calculation: (20 × 100) ÷ 100 = 20.
What is 15% of 200?
15% of 200 is 30. Calculation: (15 × 200) ÷ 100 = 30.
What is the difference between percentage and percent?
Percent is the unit (the % symbol). Percentage is the concept or the result. In everyday use the two are interchangeable.
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Last updated: . Formulas are standard and verified against manual calculation.