Updated: July 2026
What is it
The Percentage Calculator is a free online tool that solves everyday percentage calculations without you needing to memorize mathematical formulas or do the rule of three on paper. It works directly in the browser, without registration or installation, and doesn't just deliver the final result: it also shows the mathematical step by step, so you understand exactly how you arrived at that number.
Percentage means "percent" (divided by 100). It is a way of representing a fraction in which the denominator is always 100, and is a particular case of the rule of three. Understanding percentages is essential for dealing with money, discounts on purchases, interest, salary increases, rent and everyday statistics.
How to use the Percentage Calculator
The tool has 5 main modes to suit different situations in your daily life:
- X% of Y: Find out the absolute value of a percentage. Ideal for calculating commissions and tips. (Ex: What is 15% of R$200? The answer is 30.)
- X is how many % of Y: Find out the proportion that a value represents within a total. (Ex: 30 out of 150 is equivalent to how many %? The answer is 20%.)
- Variation from X to Y: Calculate the rate of increase or reduction between two numbers. Ideal for calculating inflation or price changes. (Ex: The rent went from R$1,000 to R$1,150. What was the percentage increase?)
- Add X% to Y: Add a percentage increase to a base value. Ideal for simulating taxes, adjustments and salary increases. (Ex: Add 10% tip to a R$80 bill.)
- Subtract X% from Y: Calculate the final value after a discount. Ideal for calculating promotions. (Ex: Get 20% off a R$150 blouse.)
In all modes, simply enter the two requested numbers (the calculator accepts a period or comma as a decimal separator) and the result appears immediately, along with the blue box explaining the calculation step by step.
Percentage Formulas (Step by Step)
If you want to calculate manually, here are the formulas used by our tool:
- Find the percentage of a value: Multiply the value by the percentage and divide by 100.
(Value * Percentage) / 100 - Find out the percentage rate: Divide the partial amount by the total amount and multiply by 100.
(Part / Total) * 100 - Calculate the increase or discount: Divide the difference between the final and initial value by the initial value, and then multiply by 100.
((Final - Initial) / Initial) * 100
Our percentage calculator does all these calculations automatically. Just choose the desired mode, enter the values and check the blue box with a detailed explanation of how the calculation was made, without having to use the rule of three or formulas on hand.