Percentage Calculator
Three everyday percentage problems in one tool: the percent of a value, the percent one number is of another, and percentage increase or decrease.
Updated September 2026 · Written and verified by Akash Pandey
Percentage Calculator
How to use the percentage calculator
- Pick a mode: "What is X% of Y?", "X is what % of Y?" or "% change from A to B".
- Fill in the fields and the result updates live.
- The worked equation is shown under the result so you can see exactly how it was computed.
A full explainer with examples lives on the percentage calculator page at the site root - this tool is the quick-answer companion.
Frequently asked questions
How do I work out a percentage?
Convert the percentage to a fraction of 100 and multiply: 15% of 200 = 15/100 × 200 = 30. The tool does exactly this and shows the working.
How do I calculate percentage change?
Divide the difference by the original value and multiply by 100: (B − A) ÷ A × 100. A positive result is an increase, negative a decrease.
What is a reverse percentage?
Finding the original before a percentage was applied - e.g. if 64 is 80% of something, the original is 64 ÷ 0.8 = 80. Useful for pre-tax or pre-discount prices.
Can I use it for discounts?
Yes - "What is 25% of 68?" followed by a subtraction, or use the change mode to see how much a price moved.
Is it accurate?
Results are computed to up to 12 significant digits, far beyond what a price or markup needs.
What percentage calculations can I solve with this tool?
You can solve: What is X% of Y?, X is what percent of Y?, and what is the percentage increase or decrease from X to Y?
How do I calculate percentage change between two values?
Subtract the old value from the new value, divide by the old value, and multiply by 100: ((New - Old) / Old) * 100.
Can percentage calculations handle negative numbers?
Yes. Both percentage values and base numbers can be positive or negative, with accurate mathematical sign handling.