Percentage Calculator
A flexible percentage calculator for everyday UK use — discounts in the sales, pay rises, mortgage rate changes, VAT add-ons, or working out what percentage one number is of another. Pick the operation, plug in the numbers, and get the answer plus the working so you can sanity-check it.
How is this calculated?
The calculator handles four common operations. Percentage of a value: V × p/100. Reverse (find the whole given a part and percent): part / (p/100). Percentage change: (new − old) / old × 100. Percentage increase or decrease: V × (1 ± p/100). VAT-style additions and removals are special cases — adding 20% VAT multiplies by 1.2; removing it divides by 1.2 (not by 0.8, a common error).
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. So 15% of £80 is 80 × 15 ÷ 100 = £12. The shortcut: move the decimal in the percentage two places left (15% → 0.15) and multiply: 80 × 0.15 = £12.
How do I work out percentage change?
(New − Old) ÷ Old × 100. If your salary rises from £45,000 to £48,500, that's (48,500 − 45,000) ÷ 45,000 × 100 = 7.78%. A negative answer is a decrease. Always divide by the original value, not the new one.
Why isn't a 20% drop reversed by a 20% rise?
Because the base changes. £100 down 20% is £80; up 20% from £80 is only £96. To recover from a 20% fall you need a 25% rise. This bites investors hard — losses hurt more than equivalent-percentage gains help.
How do I remove VAT from a price?
Divide by 1.2 (for the standard 20% rate), not by 0.8. A £120 gross price is 120 ÷ 1.2 = £100 net, with £20 of VAT. The reduced 5% rate divides by 1.05; the zero rate is just the price itself. HMRC publishes the current rates on gov.uk.
Last updated: May 2026 · Rates sourced from HMRC