About the Percentage Calculator
Tezmy's Percentage Calculator answers the four percentage questions people ask most, all on one page: what is X% of a number, what percent one number is of another, how much something went up or down in percent, and what a number becomes after adding or subtracting a percentage. It is ideal for discounts, tips, tax, exam marks, price changes and business growth. Answers update as you type.
Updated October 2026
How to use the Percentage Calculator
- 1Pick the calculator that matches your question.
- 2Type your numbers into the boxes. Decimals and commas are fine.
- 3Read the answer in the blue box. It updates instantly.
- 4For a discount, use “Add or subtract a percentage” with a negative percent, like −20.
The four percentage formulas
- X% of a number: multiply the number by X and divide by 100. For example, 20% of 150 = 150 × 20 ÷ 100 = 30.
- What percent A is of B: divide A by B and multiply by 100. For example, 45 out of 60 = 45 ÷ 60 × 100 = 75%.
- Percentage change from A to B: (B − A) ÷ A × 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = a 25% increase.
- Add or subtract a percentage: multiply by (1 + X ÷ 100). Adding 15% to 200 gives 200 × 1.15 = 230; subtracting 15% gives 200 × 0.85 = 170.
Everyday examples
- Exam marks: you scored 68 out of 80. That's 68 ÷ 80 × 100 = 85%.
- Shopping: a 25% discount on a 1,200 price saves 300, so you pay 900.
- Salary: a raise from 40,000 to 43,000 is a 7.5% increase.
- Tips and tax: add 10% to a 56.00 bill and the total is 61.60.
- Business: sales dropped from 500 to 420, a 16% decrease.
Percentage points vs percent
If an interest rate goes from 4% to 5%, it rose by 1 percentage point, but by 25% in relative terms (because 1 is a quarter of 4). News reports and exam questions often mix these up, so check which one is being asked. The change calculator here always gives the relative change in percent.
One more common trap: a 50% drop followed by a 50% rise doesn't bring you back to the start. 100 falls to 50, and 50% of 50 is only 25, so you end at 75.
Tips for quick mental maths
10% is the number with the decimal point moved one place left (10% of 250 is 25), and 5% is half of that. 1% is the decimal moved two places. Build other percentages from these: 15% = 10% + 5%, and 20% = 10% × 2. Percentages also work both ways: 8% of 50 is the same as 50% of 8, which is 4. Many percentage questions come from a price, so the Discount Calculator and the VAT Calculator give the final amount in one step. For school marks, the GPA Calculator turns grades into one score, and the Average Calculator finds the mean of a list of numbers.
Features
- Four calculators in one
- Instant answers as you type
- Handles decimals, commas and negative numbers
- Shows increase or decrease clearly
- Works on phone and desktop
- No ads in the way of your answer
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 150 is 0.20 × 150 = 30.
How do I work out a percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 45 out of 60 is 45 ÷ 60 × 100 = 75%.
How do I take a discount off a price?
Use “Add or subtract a percentage” and enter the discount as a negative number. A $50 item with 20% off is 50 plus −20%, which equals $40.
Why can't it calculate a change from zero?
A percentage change divides by the starting value. If the starting value is 0 the change is undefined, so there is no meaningful percentage.
How do I calculate the percentage of marks?
Divide the marks you got by the total marks and multiply by 100. For example, 420 out of 500 is 420 ÷ 500 × 100 = 84%. Use the second calculator, “is what % of”.
How do I calculate a percentage decrease?
Subtract the new value from the old one, divide by the old value and multiply by 100. The “From … to …” calculator does this for you and shows the result as, for example, ▼ 16% decrease.
How do I reverse a percentage to find the original price?
Divide by (1 + the percentage ÷ 100). If a price including 20% tax is 120, the price before tax is 120 ÷ 1.2 = 100.