What does the Percentage Calculator do?

Calculate percentages, percentage increase/decrease, and find what percentage one number is of another. All calculations are performed in your browser using official UK rates and thresholds.

Is this calculator free to use?

Yes. All calculators on Calks.uk are completely free to use. No account or registration is required. All calculations run in your browser — no data is collected.

Can I use this on my phone?

Yes. All our calculators are fully responsive and work on smartphones, tablets and desktop computers. The interface adapts to your screen size automatically.

Percentage Calculator

Calculate percentages, percentage increase/decrease, and find what percentage one number is of another.

Last updated: April 2026 · Source: BBC Bitesize — Percentages

What is X% of Y?

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Percentage Change

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Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

Percentages express a number as a fraction of 100. This calculator handles four common operations: find X% of a number, find what percentage one number is of another, calculate the percentage change between two values, and reverse-calculate the original from a percentage result.

Percentage change is widely used in finance, statistics and everyday comparisons. The formula is: ((New − Old) ÷ Old) × 100. A positive result means an increase; a negative result means a decrease. The calculator displays both the direction and magnitude clearly.

Reverse percentage is useful for VAT-inclusive prices or sale items. If you know the final value after a percentage increase or decrease, the calculator finds the original amount before the change was applied.

Example: Various percentage calculations

15% of £240 = £36
£36 is what % of £240? Answer: 15%
Percentage change from £200 to £240: +20%
If £240 includes a 20% increase, the original was £240 ÷ 1.20 = £200

Source: BBC Bitesize — Percentages

Frequently Asked Questions

What does the Percentage Calculator do?: Calculate percentages, percentage increase/decrease, and find what percentage one number is of another. All calculations are performed in your browser using official UK rates and thresholds.
Is this calculator free to use?: Yes. All calculators on Calks.uk are completely free to use. No account or registration is required. All calculations run in your browser — no data is collected.
Can I use this on my phone?: Yes. All our calculators are fully responsive and work on smartphones, tablets and desktop computers. The interface adapts to your screen size automatically.