Percentage Calculator

Three common percentage calculations

Percentages express a value as parts per hundred. This calculator covers the three forms people use most often: finding a percentage of an amount, expressing one number as a percentage of another, and measuring percentage change.

What is X% of Y?

Convert the percentage to a decimal, then multiply it by the amount:

Result = (percentage ÷ 100) × amount

For example, 15% of 80 is (15 ÷ 100) × 80 = 12.

X is what percent of Y?

Divide the part by the whole and multiply by 100:

Percentage = (part ÷ whole) × 100

For example, 18 is 30% of 60 because (18 ÷ 60) × 100 = 30%.

Percentage increase or decrease

Subtract the original value from the new value, divide by the absolute original value, and multiply by 100:

Percentage change = ((new − original) ÷ |original|) × 100

A positive result is an increase and a negative result is a decrease. Percentage change from an original value of zero is undefined because division by zero is not possible.

Tips for accurate results

• Enter numbers without percent signs or thousands separators.
• Results are calculated without intermediate rounding, then displayed with up to six decimal places.
• A percentage decrease can exceed 100% when a positive value crosses below zero.
• Percentage points and percent change are different. Moving from 20% to 25% is an increase of 5 percentage points, or a relative increase of 25%.

Frequently asked questions

How do I add a percentage to a number?

Multiply the number by 1 + percentage ÷ 100. To add 20% to 50, calculate 50 × 1.2 = 60.

How do I subtract a percentage from a number?

Multiply the number by 1 − percentage ÷ 100. To subtract 20% from 50, calculate 50 × 0.8 = 40.

Why can reversing a percentage change give a different result?

The starting value changes. A 20% increase from 100 produces 120, but a 20% decrease from 120 produces 96. Returning from 120 to 100 requires a decrease of about 16.67%.