UtilityBaseCalculators
Percentage Calculator
What is X% of Y, percentage change, and 'X is what % of Y', solved live.
Updated February 8, 2026
How to use the percentage calculator
- 1Pick the question you're answering from the three modes.
- 2Type your numbers, the result and formula appear instantly.
- 3Copy the result if needed.
Common uses
- Work out discounts, tips, and tax.
- Convert test scores to percentages.
- Measure price or metric changes over time.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage divided by 100. For example, 15% of 80 is 80 × 0.15 = 12. The first calculator mode does this live.
How is percentage change calculated?
Percentage change = (new − old) ÷ old × 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = a 30% increase. A negative result means a decrease.
Why is a 50% increase not undone by a 50% decrease?
Because the base changes. 100 increased by 50% is 150; decreasing 150 by 50% gives 75, not 100. Percentage changes always apply to the current value, not the original.
Can I use this for discounts and tips?
Yes. 'what is X% of Y' is exactly the discount/tip calculation. For the price after a discount, subtract the result from the original price.
About this tool
The percentage calculator answers the three percentage questions everyone actually asks: what is X% of Y (tips, discounts, tax), X is what percent of Y (scores, proportions), and the percentage change from A to B (price increases, growth). Each mode shows the result live as you type along with the formula used, so you can sanity-check the math instead of trusting a black box. No app, no signup, just numbers in, answer out.
Like most tools on UtilityBase, the percentage calculator runs entirely in your browser. Nothing you enter is uploaded or stored on a server. It's free to use with no account required. Browse more calculators here.
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