How do I calculate a percentage of a number?

To find X% of Y, multiply Y by X and divide by 100. Example: 15% of £280 = 280 × 15 ÷ 100 = £42. Equivalently, multiply by the decimal: 280 × 0.15 = 42.

How do I calculate percentage change?

Percentage change = ((New value − Old value) ÷ Old value) × 100. If a salary rises from £35,000 to £37,450, the change is ((37,450 − 35,000) ÷ 35,000) × 100 = 7.0%. A negative result means a decrease.

How do I add VAT to a price?

To add 20% VAT, multiply the net price by 1.20. Example: £850 × 1.20 = £1,020 (gross including VAT). To find just the VAT amount: £850 × 0.20 = £170. Alternatively, use our VAT calculator for a full breakdown of net, VAT and gross amounts.

How do I work out a percentage tip?

Multiply the bill by the tip percentage divided by 100. Example: 15% tip on a £65 bill = £65 × 0.15 = £9.75. A common UK custom is to tip 10–15% in restaurants. Some establishments include a service charge — check the bill before tipping.

Percentage Calculator UK | % Of, % Change, Increase & Decrease

How Percentages Work — Quick Reference

What is X% of Y?

Multiply Y by X ÷ 100. Example: 15% of £280 = 280 × 0.15 = £42. Useful for: VAT amounts, discounts, commission, tips, pension contributions.

X is what % of Y?

Divide X by Y and multiply by 100. Example: £42 of £280 = (42 ÷ 280) × 100 = 15%. Useful for: finding what proportion one number is of another — your tax rate, your savings rate, the deposit percentage on a house.

Percentage change

((New − Old) ÷ Old) × 100. Example: salary rising from £35,000 to £37,450 = ((37,450 − 35,000) ÷ 35,000) × 100 = 7%. A negative result means a decrease. Useful for: pay rises, investment returns, inflation comparisons.

Percentage increase / decrease

Increase: multiply by (1 + rate/100). Decrease: multiply by (1 − rate/100). Example: £45,000 increased by 5.5% = £45,000 × 1.055 = £47,475. A 20% discount on £65 = £65 × 0.80 = £52.

Common UK percentage shortcuts

20% VAT: Multiply by 1.2 to add VAT. Divide by 1.2 (or multiply by 5 ÷ 6) to remove it.
5% VAT: Multiply by 1.05 to add. Divide by 1.05 to remove. VAT is 1/21 of the gross price.
10% tip: Divide by 10. A 15% tip: find 10%, then add half again.
Tax bands: Basic rate = 20% on income between £12,570 and £50,270. Higher = 40% above £50,270.

Worked Examples

VAT calculation

Net invoice£850

VAT rate20%

20% of £850£170

Gross (inc. VAT)£1,020

Salary pay rise

Current salary£45,000

Pay rise5.5%

Increase£2,475

New salary£47,475

Retail discount

Original price£65

Discount20%

Saving£13

Sale price£52

Frequently Asked Questions

Multiply the number by the percentage divided by 100. Example: 15% of £280 = 280 × (15÷100) = 280 × 0.15 = £42. Equivalently: 10% of £280 is £28 (divide by 10), so 15% = £28 + £14 = £42.

Percentage change = ((New − Old) ÷ Old) × 100. If a salary rises from £35,000 to £37,450: ((37,450 − 35,000) ÷ 35,000) × 100 = (2,450 ÷ 35,000) × 100 = 7.0%. A negative result indicates a decrease. This formula works for any quantity — prices, investments, populations.

To add 20% VAT: multiply by 1.20. Example: £850 × 1.20 = £1,020. To remove 20% VAT from a gross price: divide by 1.20. Example: £1,020 ÷ 1.20 = £850. For 5% VAT: multiply by 1.05 to add, divide by 1.05 to remove. The VAT element in a 5% gross price is always 1/21 of the gross.

Multiply the bill by the tip percentage ÷ 100. Example: 15% on a £65 bill = £65 × 0.15 = £9.75. Quick mental method: 10% of £65 = £6.50; 5% = £3.25; 15% = £6.50 + £3.25 = £9.75. Some UK restaurants include a discretionary 12.5% service charge — always check the bill before adding a further tip.

Percentage Calculator