Percentage Calculator
Work out X% of Y, what percent X is of Y, and the percentage change between two numbers.
Why use this tool?
Solve the three common percentage questions: what is X% of Y, X is what percent of Y, and the percentage change from one number to another.
How to use it
- Pick the type of calculation.
- Enter the two numbers.
- Read the result.
The three percentage questions
Almost every percentage problem is one of three questions. What is X% of Y? Multiply: Y × X ÷ 100, so 15% of 80 is 12. X is what percent of Y? Divide: X ÷ Y × 100, so 18 out of 72 is 25%. What is the percentage change from A to B? (B − A) ÷ A × 100, so a price going from 50 to 65 is a 30% increase.
Choose the matching calculation type in the tool and enter the two numbers; the result appears immediately.
Why increases and decreases don't cancel out
A percentage change is always measured from the starting value. Going from 50 to 65 is +30%, but going back from 65 to 50 is only −23.08%, because the second change is measured from the larger number.
The same effect makes successive changes multiply rather than add. A 10% rise followed by a 10% fall leaves you 1% lower than where you started (1.10 × 0.90 = 0.99). Two discounts of 20% and 10% give 28% off in total, not 30%.
Everyday uses
Shopping: a 25% discount on 120 saves 30, so you pay 90. Tips and tax: 18% of a 64 bill is 11.52. Grades: 42 correct out of 50 is 84%. Growth: a website that went from 1,200 to 1,500 visitors a month grew by 25%.
Percent and percentage points are not the same. If an interest rate rises from 4% to 5%, it went up by one percentage point, which is a 25% increase in the rate itself. News reports mix these up often.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. 7% of 250 is 250 × 7 ÷ 100 = 17.5.
How do I work out a percentage decrease?
Use the percentage change formula; a negative result is a decrease. From 80 to 60: (60 − 80) ÷ 80 × 100 = −25%.
How do I reverse a percentage, like finding the price before tax?
Divide by (1 + rate). If 115 includes 15% tax, the pre-tax price is 115 ÷ 1.15 = 100. Subtracting 15% of 115 would give the wrong answer (97.75).