Percentage Calculator
What is X% of Y?
Percentage Change
X% of Y = ?
X is what % of Y?
The four percentage formulas explained
X% of Y — multiply Y by X and divide by 100. Used for discounts, tips, and tax calculations.
Percentage change — subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase, a negative result is a decrease. This is the formula used for pay rises, investment returns, and price changes.
X is what % of Y — divide X by Y and multiply by 100. Useful for exam scores, market share, or working out what proportion something represents.
Worked examples
What is 15% of £84 (restaurant tip)?
84 × 15 ÷ 100 = £12.60
A £60 item is reduced by 25% — new price?
60 − (60 × 25 ÷ 100) = £45
Your salary rose from £30,000 to £33,000 — what % increase?
(33,000 − 30,000) ÷ 30,000 × 100 = 10%
You scored 42 out of 50 on a test — what percentage?
42 ÷ 50 × 100 = 84%
A common mistake to avoid
Percentage increases and decreases aren't symmetrical: increasing £100 by 20% gives £120, but decreasing £120 by 20% gives £96 — not back to £100. This is because the second calculation applies 20% to a larger starting number. Keep this in mind when comparing "before and after" figures, such as sale discounts or investment losses and gains — see our Compound Interest Calculator for how this compounds over time.
Related tools
100% private — your figures are calculated in your browser and never stored or shared.
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. E.g. 20% of 150 = 150 × 20 / 100 = 30.
How do I calculate a percentage increase?
Subtract the original from the new value, divide by the original, then multiply by 100. E.g. 80 to 100 = (100-80)/80 × 100 = 25% increase.
What is percentage used for?
Percentages are used everywhere — tips, discounts, tax rates, investment returns, exam scores, and statistics.
Be first to know when we launch new tools
Join 2,400+ UK readers who get early access to new calculators, expert financial guides, and free resources — straight to their inbox.
- First to hear about new calculators
- Exclusive money-saving tips
- Free UK Tax Cheatsheet 2026/27
Not Financial Advice: This calculator is for informational and educational purposes only. Results are estimates and do not constitute financial advice, recommendations, or regulated advice. We are not authorised or regulated by the Financial Conduct Authority (FCA). Always consult a qualified financial adviser for personalised advice. Tax treatment depends on your individual circumstances and may change. Tax laws and rates may change. Past performance does not guarantee future results.
