Percentage Calculator
A simple, reliable percentage calculator for everyday money questions: what is 20% of £500, what percentage of my income is my rent, or by how much has a price changed?
Pick a mode, enter your numbers, and the result appears instantly.
How the calculation works
We believe numbers should be transparent. Here is the formula behind this calculator.
Worked example
Worked example: finding 20% of £500
Important assumptions
- Percentages are based on the values you enter as plain numbers (they can be money or any quantity).
- Percentage change is measured against the starting value.
Frequently asked questions
How do I calculate a percentage in my head?
Divide by 100 to get 1%, then multiply. For 20% of £500: 1% is £5, so 20% is £100. For 10%, just move the decimal point one place.
How do I work out percentage change?
Divide the difference between the new and old value by the old value, then multiply by 100. A price rising from £80 to £100 is a 25% increase ((100 − 80) ÷ 80 × 100).
Is this calculator useful for VAT and discounts?
Yes. VAT is a percentage of a price, and discounts are a percentage off. See our VAT calculator for VAT-specific maths.
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Related guides
New to the topic? Browse the guides section for plain-English explainers on personal finance, including worked examples and tips.
Browse financial guidesThese calculations are estimates for guidance only and are not professional financial, tax or legal advice. UK rates and rules change, so always verify important figures with official GOV.UK / HMRC information or speak to a qualified professional. See our full disclaimer.