Percentage Calculator
The Percentage Calculator answers the everyday percentage questions in one place: what is X% of Y, what percentage one number is of another, and the percentage increase or decrease between two values. Enter your numbers to get an instant, clearly labelled answer.
The three percentage questions
Almost every percentage problem is one of three types. Finding a part: what is 15% of 200? Finding a rate: 30 is what percent of 200? Finding a change: what is the percentage increase from 200 to 260? Once you know which type you have, the maths is quick.
The formulas
Part of a whole: X% of Y = X ÷ 100 × Y. One number as a percentage of another: A ÷ B × 100. Percentage change: (New − Old) ÷ Old × 100, positive for an increase and negative for a decrease.
A worked example
15% of 200 is 0.15 × 200 = 30. Going the other way, 30 is 30 ÷ 200 × 100 = 15% of 200. And if a price rises from 200 to 260, the change is (260 − 200) ÷ 200 × 100 = 30% increase. The same three formulas cover discounts, tips, exam marks, interest and growth rates.
Handy shortcuts
To find 10% of anything, just move the decimal one place. Percentages are reversible, so 8% of 50 equals 50% of 8, whichever is easier to work out in your head. And remember that a percentage increase followed by the same percentage decrease does not return you to the start, because each step works on a different base.
How to use
- Enter your details in the fields above. The Percentage Calculator accepts everyday values and checks them as you type.
- Press the action button (or just start typing for live tools) to run the calculation.
- Read your result, along with any supporting figures, in the clearly labelled result box.
- Use Copy result to grab the answer, Reset to start again, or Copy link to share this tool.
Why use this tool
Finance Wave built the Percentage Calculator to be genuinely useful: it validates your input so you never see a broken result, formats numbers for your region automatically, and stays readable in both light and dark mode. Because everything happens on your device, it is private by design and keeps working even without an internet connection once the page has loaded.