Percentage Formula
Most percentage questions use one of a few simple formulas. Choose the formula that matches the reference value in your problem.
Basic percentage
percentage = (part / whole) x 100
Percent of a number
result = (percent / 100) x value
Percent increase formula
((new value - old value) / old value) x 100
Percentage decrease formula
((new value - old value) / old value) x 100
Percentage change formula
((new value - old value) / |old value|) x 100
Percentage difference
|a - b| / ((|a| + |b|) / 2) x 100
Discount formula
sale price = original price - (original price x discount / 100)
Worked Examples
20% of 150: 20 / 100 x 150 = 30.
30 is what percent of 120: 30 / 120 x 100 = 25%.
From 80 to 100: (100 - 80) / 80 x 100 = 25%.
Which formula should you use?
Use percent of a number when you know the percent and the base value, such as 15% of 80.
Use percentage change when one value clearly comes before the other, such as old price to new price.
Use percentage difference when comparing two values without treating either one as the original value.
Use the discount formula when you know an original price and a percent off amount.
Other Calculators
Simple tools for nearby percentage questions.
Percentage Calculator
Calculate a percentage, percent of a number, or part of a whole.
Percentage Increase Calculator
Find percent growth from one value to another.
Percentage Difference Calculator
Compare two values using percentage difference.
Percentage Change Calculator
Calculate increases and decreases between old and new values.
Percentage Decrease Calculator
Find percent decrease from an original value to a lower value.
Discount Calculator
Find sale prices and savings from a discount percent.
FAQ
The basic formula is part / whole x 100.
Convert the percent to a decimal by dividing by 100, then multiply by the number.
Percent increase is ((new value - old value) / old value) x 100 when the old value is positive.
Percentage difference is |a - b| / ((|a| + |b|) / 2) x 100.