Percentage Formulas
(X ÷ 100) × Y(X ÷ Y) × 100X ÷ (Y ÷ 100)((New − Old) ÷ |Old|) × 100|A − B| ÷ ((|A| + |B|) ÷ 2) × 100Value × (1 ± Percentage ÷ 100)Final ÷ (1 + Percentage ÷ 100)Final ÷ (1 − Percentage ÷ 100)Percentage Change vs. Percentage Difference
Percentage change has a starting point. It answers questions such as “sales went from 80 to 100, what was the percentage increase?” The original value is the denominator.
Percentage difference is useful when neither value is naturally the starting point. It compares the absolute difference with the average magnitude of the two values.
Percentage Calculator FAQ
How do I calculate a percentage of a number?
Convert the percentage to a decimal by dividing it by 100, then multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 ÷ 150 × 100 = 20%.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. A positive result is an increase and a negative result is a decrease.
How do I find the original value before a percentage increase or discount?
Work backward using division. After an increase, divide the final value by 1 + the percentage as a decimal. After a decrease, divide by 1 − the percentage as a decimal.
What happens if the original value is zero?
Standard percentage change from zero is undefined because the formula requires division by the original value. The calculator shows an error rather than returning a misleading percentage.