Percentage Calculator
Five percentage calculations on one page, with the math shown so you can check it.
- Never leaves your device
- No sign-up
What is X% of a number
Fill in both fields.
X is what percent of Y
Fill in both fields.
Increase a number by X%
Fill in both fields.
Take X% off a price
Fill in both fields.
Percent change between two values
Fill in both fields.
Quick answer: To calculate a percentage, pick the calculation and fill in the two fields: X% of a value, X is what percent of Y, increase, discount or percent change between two values. The result appears instantly, along with the formula used.
How to do it in 3 steps
- 1Choose the type of percentage calculation.
- 2Fill in the two values.
- 3Read the result and the math right below it.
Why use Pronto Arquivo
Five calculations on one screen
X% of a value, ratio, increase, discount and percent change, without switching pages.
Math explained
Every result shows the formula, handy for studying or double-checking.
Decimals welcome
Works with decimal values like 1,250.90 as well as whole numbers.
Fast on mobile
Numeric keypad and the result on the same screen.
Guides
How to calculate percentages in your head
10% is dividing by 10; 5% is half of 10%; 1% is dividing by 100. Example: 15% of 80 = 8 (10%) + 4 (5%) = 12.
Stacked discounts
Two 10% discounts don't add up to 20%: 100 × 0.9 × 0.9 = 81, so 19% off in total. Run the calculator twice.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. Example: 20% of 150 = 150 × 20 ÷ 100 = 30.
How do I find what percent one number is of another?
Divide the part by the total and multiply by 100. Example: 30 out of 150 = 30 ÷ 150 × 100 = 20%.
How do I calculate a discount?
Price × (1 − discount ÷ 100). Example: $200 with 15% off = 200 × 0.85 = $170.
How do I calculate percent change?
(New − Original) ÷ Original × 100. Example: from 50 to 65 = +30%.
How do I calculate a percentage increase?
Value × (1 + increase ÷ 100). Example: 1,000 with an 8% increase = 1,080.