Percentage Calculator
Calculator
This percentage calculator covers three common problems: finding a percentage of a number (e.g. 15% of 200), finding what percentage one number is of another (e.g. 30 is what % of 120), and calculating the percentage increase or decrease between two values (e.g. from 80 to 100). Select the mode that matches your question.
Formula
Formula
Mode 1: result = (X / 100) × Y | Mode 2: result = (X / Y) × 100 | Mode 3: result = ((Y − X) / |X|) × 100
Mode 1 ('What is X% of Y?'): divide X by 100, then multiply by Y. Mode 2 ('X is what percent of Y?'): divide X by Y and multiply by 100. Mode 3 ('Percentage change from X to Y'): subtract X from Y to get the absolute change, then divide by the absolute value of X and multiply by 100. A positive result is an increase; a negative result is a decrease.
Worked example
A product's price increased from $80 to $100. What is the percentage increase?
- 1.Select mode: 'Percentage increase/decrease from X to Y'
- 2.X = 80 (original price), Y = 100 (new price)
- 3.Absolute change = 100 − 80 = 20
- 4.% change = (20 / 80) × 100 = 0.25 × 100 = 25%
The price increased by 25%.
Assumptions and limitations
- Mode 1 ('What is X% of Y?'): both X and Y must be valid numbers.
- Mode 2 ('X is what percent of Y?'): Y must not be zero.
- Mode 3 (percentage change): X (the starting value) must not be zero.
- Negative values are valid — e.g., losses, temperatures below zero.