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 everything 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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