Percentage calculator with the working shown
Five common percentage questions in one place: what is 15% of 80, what percent is 12 of 60, the percentage change from 50 to 65, and a number increased or decreased by a percentage. Every answer shows the formula used.
How to use the Percentage Calculator
- Pick the question type.
- Enter A and B.
- Click Calculate to see the result and the formula.
The five formulas
| Question | Formula | Example |
|---|---|---|
| What is A% of B? | A ÷ 100 × B | 15% of 80 = 12 |
| A is what % of B? | A ÷ B × 100 | 12 is 15% of 80 |
| % change from A to B | (B − A) ÷ |A| × 100 | 50 → 65 = +30% |
| B increased by A% | B × (1 + A/100) | 80 + 15% = 92 |
| B decreased by A% | B × (1 − A/100) | 80 − 15% = 68 |
Percentage points vs percent
If an interest rate rises from 4% to 5%, it has risen by one percentage point but by 25 percent. News reports often blur the two; use "percentage points" for differences between two percentages and "percent" for relative change.
Why a 20% drop then a 20% rise does not get you back
Percent changes compound on the new base. £100 down 20% is £80; £80 up 20% is £96, not £100. To undo a 20% drop you need a 25% rise. The same asymmetry is why a shop's "50% off, then 50% off again" is 75% off, not 100%.
Tips, tax and discounts
Use "B increased by A%" for adding VAT or a tip (£40 meal + 12.5% = £45) and "B decreased by A%" for discounts (£60 jacket − 30% = £42). To find the pre-tax price from a total, divide by (1 + rate): £120 including 20% VAT is £100 net.
Frequently asked questions
How do I calculate percentage increase?
Subtract the old value from the new, divide by the old value, multiply by 100. Choose “% change from A to B”.
What is 20% of 150?
20 ÷ 100 × 150 = 30.
How do I remove VAT from a price?
Divide the gross price by 1.2 for 20% VAT. £120 ÷ 1.2 = £100.
Privacy
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Last updated 2026-09-23.