Percentage Calculator
What is x% of y, reverse percent, and increase or decrease a number by p%. For old value → new value, use percentage change.
What is x% of y?
15% of 80
12
From an old value to a new value? Use the percentage change calculator.
More: reverse percent and apply ±p%
x is what % of y?
12 is what % of 80
15%
Increase or decrease a number by p%
After applying p%
92
- Increase by 15%92
- Decrease by 15%68
This page answers “what is x% of y”, “x is what percent of y”, and “increase or decrease a number by p%”. For the change from an old value to a new value (60 → 72), use the percentage change calculator.
Formula
x% of y = (x / 100) × y. “x is what percent of y” = (x / y) × 100. Increase: new = old × (1 + p / 100). Decrease: new = old × (1 − p / 100).
How to calculate
- Decide which question you are asking: part of a whole, reverse percent, or apply a percent to a number.
- Convert the percent to a decimal by dividing by 100 (15% → 0.15).
- Multiply or divide as in the formula. Check the sign: a decrease uses 1 − p/100.
Example
15% of 80 is (15 / 100) × 80 = 12. 12 is (12 / 80) × 100 = 15% of 80. Increasing 80 by 15% is 80 × 1.15 = 92.
Common mistake
“Increase 80 by 15%” is not the same as “80 increased to 15% of itself”. The first is 92; the second is 12. Percent of a number and percent change between two numbers are different tools.
FAQ
What is 15% of 80?
12. Compute (15 / 100) × 80 = 12.
How do I find what percent 12 is of 80?
15%. Compute (12 / 80) × 100 = 15.
How do I increase a number by a percentage?
Multiply by (1 + p / 100). 80 increased by 15% is 80 × 1.15 = 92. To go from an old value to a new value and get the percent, use percentage change.
How do I decrease a number by a percentage?
Multiply by (1 − p / 100). 80 decreased by 15% is 80 × 0.85 = 68.