Percentage Calculator
Calculate percentages easily — find X% of a number, percentage change, increase and decrease. Four calculators in one tool.
What is X% of Y?
Example: What is 15% of 200? → 30. Useful for calculating tips, discounts, or tax amounts.
X is what % of Y?
Example: 30 is what % of 200? → 15%. Handy for working out exam scores, savings rates, or conversion rates.
Percentage change
Example: From 80 to 100 → +25%. Great for comparing prices, salaries, or tracking progress over time.
Increase/decrease by %
Example: 200 ± 15% → 230 or 170. Useful for adding VAT, applying discounts, or calculating pay rises.
The Four Percentage Calculations You Actually Use
Almost every percentage problem fits one of four shapes. What is X% of Y? (15% of £80 = £12.) X is what % of Y? (£12 is what % of £80? = 15%.) Percentage change from old to new ((new - old) / old × 100). And increase or decrease a value by a percentage (£80 increased by 15% = £92). The calculator gives you all four side by side so you do not have to remember which formula goes with which question.
The single most common mistake is confusing 'percentage of' with 'percentage change'. £100 increased by 25% is £125; £125 decreased by 25% is £93.75, not £100. Percentage change is asymmetric because the base shifts. To reverse a 20% increase, you decrease by 16.67% (because 1 / 1.2 = 0.833).
VAT, Tips, Discounts, and Pay Rises
Adding 20% VAT to a £50 net price: 50 × 1.2 = £60. Removing 20% VAT from a £60 gross price: 60 / 1.2 = £50 (not 60 × 0.8, which gives £48 and is the wrong answer). A 15% tip on a £40 meal: 40 × 1.15 = £46. A 30% sale discount on a £80 jumper: 80 × 0.7 = £56. A 4% pay rise on a £35,000 salary: 35,000 × 1.04 = £36,400.
When you have multiple percentages stacked, calculate them one at a time. A 20% discount followed by an extra 10% off is not 30% off; it is 1 - (0.8 × 0.9) = 28% off. The order does not matter as long as you multiply the multipliers together. If the calculation involves your salary, [UK Tax Calculator](/uk-tax-calculator) handles the rest of the deductions.
Common Percentage Calculations
| Question | Calculation | Answer |
|---|---|---|
| 20% of £150 | 150 × 0.20 | £30 |
| £45 is what % of £180? | (45 / 180) × 100 | 25% |
| Change from 80 to 100 | ((100 - 80) / 80) × 100 | +25% |
| £200 + 17.5% | 200 × 1.175 | £235 |
| Remove 20% VAT from £120 | 120 / 1.20 | £100 |
Frequently Asked Questions
How do I work out a percentage in my head?
Find 10% first by dividing by 10, then scale. 15% of £80: 10% is £8, half of that is £4, so 15% is £12. 25% of anything is the same as dividing by 4. 5% is half of 10%. Stacking these mental steps usually gets you to a sensible answer faster than typing it in.
Why is removing a percentage not the same as the negative version?
Because the base changes. £120 minus 20% VAT means the £120 already includes the VAT. The original net was 120 / 1.2 = £100, not 120 × 0.8 = £96. Always think about whether the percentage is being added on top or already baked in.
What is the difference between percentage change and percentage difference?
Percentage change has a clear before and after (a 20% pay rise from £30,000 to £36,000). Percentage difference compares two values without one being the baseline (the difference between £30,000 and £36,000 as a percentage of their average is about 18.18%). Use change for time-based comparisons, difference for symmetrical ones.
How do I add 20% VAT correctly?
Multiply the net price by 1.20. £50 × 1.20 = £60. To remove VAT from a gross price, divide by 1.20: £60 / 1.20 = £50. The common slip is multiplying by 0.80 to remove VAT, which gives the wrong answer.
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