Percent Calculator
Calculate percentages, find ratios, and determine percentage changes instantly
What Does This Tool Do?
The Percent Calculator handles the three most common percentage calculations in one convenient tool. Switch between modes to find what a given percentage of a number equals, determine what percentage one number is of another, or calculate the percentage change between two values. Results update in real time as you type, and the formula is displayed alongside the answer so you can understand the math behind it. Whether you are calculating discounts, tips, grade percentages, or growth rates, this tool gives you instant and accurate results.
How to Use
- Choose a calculation mode by clicking one of the three tabs: "What is X% of Y?", "X is what % of Y?", or "% Change from X to Y".
- Enter your numbers in the input fields. Results update automatically as you type.
- Read the result displayed prominently below the inputs, along with the formula showing how the answer was derived.
- Switch modes at any time to perform a different type of percentage calculation without losing your previously entered values.
Common Percentage Formulas
Percentage of a Number
To find X% of Y, convert the percentage to a decimal and multiply:Result = (X / 100) x Y
What Percentage Is X of Y?
Divide the part by the whole and multiply by 100:Percent = (X / Y) x 100
Percentage Change
Subtract the old value from the new, divide by the absolute old value, and multiply by 100:Change = ((New - Old) / |Old|) x 100
Percentage Increase
Add the percentage of the original value to the original:Result = Y + (X / 100) x Y
or equivalently Y x (1 + X/100)
Percentage Decrease
Subtract the percentage of the original value from the original:Result = Y - (X / 100) x Y
or equivalently Y x (1 - X/100)
Reverse Percentage
If a value is the result after an X% increase, find the original:Original = Result / (1 + X/100)
FAQ
How do I calculate a tip at a restaurant?
Use the "What is X% of Y?" mode. Enter the tip percentage (for example, 18) and the bill total. The result is the tip amount. Add it to the bill for your total.
What is the difference between percentage change and percentage difference?
Percentage change measures the relative change from an original value to a new value, with direction (increase or decrease). Percentage difference compares two values without implying that one is the starting point, using the average of both values as the denominator.
Can I use decimal percentages like 7.5%?
Yes. All input fields accept decimal numbers, so you can enter values like 7.5, 0.25, or 33.33 for precise calculations.
Why does the percentage change show a sign (+ or -)?
A positive sign indicates an increase from the original value, while a negative sign indicates a decrease. This makes it immediately clear whether the value went up or down.
What happens if the original value in percentage change is zero?
Percentage change is undefined when the starting value is zero because it would require division by zero. The calculator will display an appropriate message in that case.