How do I add a percentage to a number?

Multiply by 1 plus the percentage as a decimal. 250 increased by 12% is 250 x 1.12 = 280. Working out 12% separately and adding it gives the same answer, and multiplying is one step rather than two.

Is a 100% increase the same as doubling?

Yes. A 100% increase adds the original amount again, so the result is twice the start. A 200% increase triples it, which is where the two ways of speaking most often part company.

Math & Statisticspercentage

Percentage Increase Calculator

Increase a number by a percentage. Note that reversing this needs division, not subtraction. The reverse-percentage calculator handles that.

Also called: percent increase calculator, how much did it go up.

After the increase

1,120

1,000 increased by 12% is 1,120, an increase of 120.

Amount of the increase

120

How this is calculated

Method and background

How this is calculated

Multiply by one plus the percentage as a decimal. Increasing by 20% and then decreasing by 20% does not return you to where you started, which is the source of a surprising amount of confusion about discounts.

result = value * (1 + percent/100)

p: The increase, in percent

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

1000 up 12%

Starting value: 1,000
Increase by (%): 12

After the increase1,120

arithmetic identity

Open this example

zero increase

Starting value: 1,000
Increase by (%): 0

After the increase1,000

degenerate case

Open this example

doubling is a 100% increase

Starting value: 500
Increase by (%): 100

After the increase1,000

boundary

Open this example

Frequently asked questions

How do I add a percentage to a number?: Multiply by 1 plus the percentage as a decimal. 250 increased by 12% is 250 x 1.12 = 280. Working out 12% separately and adding it gives the same answer, and multiplying is one step rather than two.
Is a 100% increase the same as doubling?: Yes. A 100% increase adds the original amount again, so the result is twice the start. A 200% increase triples it, which is where the two ways of speaking most often part company.