How to calculate 25% of 100
1) Turn the percentage into a decimal: 25 ÷ 100 = 0.25. 2) Multiply by the number: 100 × 0.25 = 25. Shortcut: 100 × 25 ÷ 100 = 25. Adding 25% to 100 gives 125; taking 25% off gives 75.
Other percentages of 100
1% → 1 · 2% → 2 · 5% → 5 · 10% → 10 · 15% → 15 · 20% → 20 · 25% → 25 · 30% → 30 · 40% → 40 · 50% → 50 · 75% → 75
Percentage Calculator
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How to use
- 1Find the row that matches your question, e.g. “What is X% of Y?” or “% change from X to Y”.
- 2Type your numbers into that row — decimals work with a point or a comma.
- 3Read the result instantly; it updates as you type.
- 4Use the discount row to see the sale price and how much you save.
The six percentage questions
Almost every percentage problem is one of six: X% of Y (15% of 80 = 12); X is what percent of Y (12 of 80 = 15%); percentage change from X to Y ((new − old) ÷ old × 100); adding X% to Y (80 + 15% = 92); subtracting X% from Y (80 − 15% = 68); and X is Y% of what (12 is 15% of 80). Each row of the calculator answers one of them, so you never have to rearrange the formula yourself.
Percentage change vs percentage points
If an interest rate rises from 4% to 5%, that is an increase of 1 percentage point but a 25% increase in relative terms. Percentage change always divides by the starting value, which is why a 50% fall followed by a 50% rise does not bring you back to where you started: 100 → 50 → 75.
Discounts, tips and price rises
A 25% discount on £60 means paying 75% of the price: £45, saving £15. Two discounts in a row multiply rather than add — 20% off and then another 10% off is 28% off in total, not 30%. The same logic applies to tips, service charges and price increases: “add X%” multiplies by (1 + X/100).
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of 80 is 80 × 15 ÷ 100 = 12.
How do I work out a percentage increase?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 92 is (92 − 80) ÷ 80 × 100 = 15%.
How do I find the original price before a discount?
Divide the sale price by (1 − discount/100). A £45 item after 25% off was £45 ÷ 0.75 = £60. The “X is Y% of what” row does this for you.
Can I type decimals with a comma?
Yes. Both 1.5 and 1,5 are accepted.
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