Percent Calculator

How it works

Percent means per hundred, so every question here is a multiply or divide by 100. Percent change always divides by the starting value, which is why going up 50% and then down 50% doesn’t bring you back.

Example

A price goes from $80 to $92. What is the percent change?

15% increase

Steps

1. 1
   Change: 92 − 80 = 12.
2. 2
   Divide by the starting value: 12 ÷ 80 = 3/20 ≈ 0.15.
3. 3
   Multiply by 100: 15%.

More examples

What is 15% of 80?

12

Steps

1. 1
   Change 15% to a fraction of 100: 15 / 100.
2. 2
   Multiply by 80: 15 × 80 / 100 = 12.

A jacket costs $42 after 30% off, so $42 is 70% of the original. What was it?

60

Steps

1. 1
   42 is 70% of the whole, so whole × 70 / 100 = 42.
2. 2
   Divide: 42 ÷ 70 × 100 = 60.

Common mistake

After a discount, you can’t add the percent back on. If a game costs $40 after 20% off, the original is 40 ÷ 0.8 = $50, not $48.

Questions

How do I add tax or a tip?

Multiply by 1 plus the rate. A $40 bill with 8% tax is 40 × 1.08 = $43.20.

What is the difference between percent and percentage points?

Going from 20% to 25% is a rise of 5 percentage points, but a 25% increase, because 5 is 25% of 20.

How do I change a fraction to a percent?

Divide, then multiply by 100: 3/8 = 0.375 = 37.5%.

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