Percentage Calculator
Add or subtract a percentage from any number, work out what percentage one number is of another, or see the percentage change between two numbers — results appear instantly as you type, with no sign-up required.
Calculator
12.00
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%
Percentage change between two numbers
Percentage change
+25.00%
Difference
+20.00
100.00
150.00
How it's worked out
All three 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.
The small signed figure under each result is the change itself — the percentage of your number. So for “what is 15% of 80?”, enter 80 and 15 and read 12 there.
Working out what percentage one number is of another
Divide the first number by the second, then multiply by 100: (Number ÷ Total) × 100.
Percentage change between two numbers
Subtract the old value from the new one, divide by the old value and multiply by 100: (New − Old) ÷ Old × 100. A plus sign means an increase, a minus sign a decrease. If the old value is negative, its size (without the minus) is used, so a move from −100 to −50 counts as a 50% increase.
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%.
And if a price rises from 80 to 100, the difference is 20 and the percentage change is (100 − 80) ÷ 80 × 100 = +25%. Going back from 100 to 80 is a change of −20%, not −25%, because the starting value is now 100.
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 — both calculators accept negative numbers and negative percentages, for example a loss of −200. For a discount you don’t need a negative percentage: enter the price and the discount, and the “Value after the decrease” box shows the price after the discount (20% off 80 leaves 64).
How do I work out the percentage change between two numbers?
Subtract the old value from the new one, divide by the old value and multiply by 100: (New − Old) ÷ Old × 100. For a price that rose from 80 to 100: (100 − 80) ÷ 80 × 100 = 25%. The third calculator on this page does it for you: enter 80 as the old value and 100 as the new value.
Why doesn’t adding 10% and then taking 10% off bring me back to the start?
Because the second 10% is taken from a bigger number: 200 plus 10% is 220, but 220 minus 10% is 198. To get the original back from a value that already includes a percentage, divide instead of subtracting: 220 ÷ 1.10 = 200. The same works for removing VAT from a price: with 20% VAT, £120 ÷ 1.20 = £100 before VAT — not £120 minus 20%, which would give £96.
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For information only. This is not financial or tax advice. How we build and check our calculators · Report an error