Percentage Calculator — Free Online Tool
Calculate percentages, ratios, and percentage increase or decrease in seconds.
About Percentage Calculator
The Percentage Calculator handles the three most common percentage questions in one place: what is X% of Y, X is what percent of Y, and the percentage increase or decrease from one value to another. A simple mode selector switches the labels and maths to match the question you are asking.
It is great for working out tips, marks, commissions, tax portions and quick comparisons. Each answer appears instantly with no rounding surprises, and the whole tool runs in your browser so your numbers stay private.
How to Use Percentage Calculator
- Choose the calculation mode that matches your question.
- Enter the two values into the X and Y fields.
- Click "Calculate" to get the result.
- Switch modes any time to answer a different percentage question.
Key Features
Three modes: percentage of, ratio, and percentage change
Labels update automatically for the selected mode
Handles decimals and negative values
Clear result with a descriptive label
Runs entirely in your browser
Frequently Asked Questions
How do I find X% of a number?
Multiply the number by the percentage divided by 100. For example, 20% of 150 is 150 x 0.20 = 30. The "What is X% of Y" mode does this for you.
How do I work out what percent one number is of another?
Divide the first number by the second and multiply by 100. The "X is what percent of Y" mode handles this and guards against dividing by zero.
How is percentage increase or decrease calculated?
Subtract the original value from the new value, divide by the absolute original value, and multiply by 100. A positive result is an increase and a negative one is a decrease.
Why can't Y or the starting value be zero?
Dividing by zero is undefined, so for the ratio and percentage-change modes the calculator asks for a non-zero reference value.