Percentage Calculator
Add or subtract a percentage from any number, or work out what percentage one number is of another — results appear instantly as you type, with no sign-up required.
Calculator
Increase or decrease by a percentage
Value after the increase
220.00
Change: +20.00
Value after the decrease
180.00
Change: −20.00
What percentage one number is of another
As a percentage of the total
12.50%
How it's worked out
Both calculators use simple, standard percentage formulas — no hidden maths.
Increase or decrease by a percentage
The change is: Number × Percentage ÷ 100. Add that change to get the increased value, or subtract it to get the decreased value.
Working out what percentage one number is of another
Divide the first number by the second, then multiply by 100: (Number ÷ Total) × 100.
Worked example
Suppose a value of 200 increases by 10%. The change is 200 × 10 ÷ 100 = 20, so the increased value is 200 + 20 = 220, and the decreased value would be 200 − 20 = 180.
Now suppose you scored 25 marks out of a possible 200. As a percentage: (25 ÷ 200) × 100 = 12.5%.
Frequently asked questions
How is the increased or decreased value worked out?
We multiply your number by the percentage and divide by 100 to get the change, then add or subtract that change from the original number. For example, 10% of 200 is 20, so 200 plus 10% is 220, and 200 minus 10% is 180.
How do I work out what percentage one number is of another?
Divide the first number by the second, then multiply by 100. For example, to work out what percentage 25 is of 200: (25 ÷ 200) × 100 = 12.5%.
Can I use negative numbers or percentages?
Yes — the calculator also works with negative numbers and negative percentages, for example to work out a discount or a loss.
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For information only. This is not financial or tax advice.