How to calculate a percentage
A percentage is just a fraction of 100. To turn a percentage into a number you can use in a calculation, divide it by 100 — 20% becomes 0.20. The three calculators above cover the three questions people actually ask: what is a percentage of a number? What percentage is one number of another? And how much has something changed in percentage terms?
Percentage of a number
To find X% of a number, divide the percentage by 100 and multiply by the number.
This is the calculation behind discounts, tips and tax: a 15% tip on a $60 bill is (15 ÷ 100) × 60 = $9.
X is what percent of Y
To find what percent one number is of another, divide the first number by the second, then multiply by 100.
This version answers questions like "what percentage of my income is rent" or "what share of the vote did a candidate get."
Percentage increase and decrease
To find the percentage change between two numbers, subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is an increase; a negative result is a decrease.
The original value is always the base of the comparison. That's why a $20 rise on $80 is a bigger percentage than the same $20 rise on $200.
Common everyday uses
- Discounts — work out the sale price by finding the percentage off, then subtracting it.
- Tips — a quick percentage of the bill total.
- Tax — sales tax or income tax bands are percentages applied to a base amount.
- Grades and scores — points earned as a percentage of points possible.
- Pay rises and price changes — the percentage-change calculator above.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 20% of 250 is (20/100) × 250 = 50.
How do I find what percent one number is of another?
Divide the first number by the second, then multiply by 100. For example, to find what percent 40 is of 160, divide 40 by 160 to get 0.25, then multiply by 100 to get 25%.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result is a percentage increase; a negative result is a percentage decrease.
Why is percentage change based on the original number, not the new one?
Percentage change measures how big the difference is relative to where you started. Using the original value as the base keeps the measurement consistent. The same dollar change means a bigger percentage on a small starting number than on a large one.
Are my numbers saved or sent anywhere?
No. Nothing you enter leaves your device. All three calculators run entirely in your browser.