Calculators
Percentage Calculator
Find percentages, percent change, increases, and decreases.
Percentage Calculator tool
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About This Tool
Solve common percentage questions without rearranging formulas by hand. Choose the calculation type for percent of a number, part-to-whole percentage, percent increase, percent decrease, or percent change. The calculator is useful for discounts, tips, tax checks, grade calculations, finance examples, comparisons, and everyday ratios, while still showing each result as straightforward percentage arithmetic rather than a domain-specific recommendation.
How To Use It
- Choose the percentage calculation type that matches your question.
- Enter the percentage, new value, part value, or adjustment requested by the first label.
- Enter the base, whole, original value, or comparison value requested by the second label.
- Review the live result and copy it if needed.
- Use a nonzero whole value for part-to-whole ratios. Percent-change mode requires a positive original value so the increase or decrease direction is not reversed by a negative baseline.
Examples
15% of 200
Choose What is X% of Y?, enter 15 and 200, and the result is 30.
45 is what percent of 180
Choose X is what percent of Y?, enter 45 and 180, and the result is 25%.
Percent change from 80 to 100
Choose Percent change, enter 100 as the new value and 80 as the original value. The result is 25% increase.
Decrease 80 by 25%
Choose Decrease Y by X%, enter 25 and 80, and the adjusted value is 60.
Negative adjustment
Entering -10 in increase mode lowers the value by 10%, which can be useful when a signed adjustment is easier than switching modes.
Useful Notes
Choosing the right mode
Use percent of for discounts, tips, portions, or tax amounts; what percent for part-to-whole ratios; increase/decrease for adjusted totals; and percent change for before-and-after comparisons.
Percent of formula
To find X% of Y, divide X by 100 and multiply by Y. For example, 15% of 200 is 0.15 x 200 = 30.
Part-to-whole formula
To find what percent X is of Y, divide X by Y and multiply by 100. The whole or comparison value cannot be zero because division by zero is undefined.
Percent change formula
Percent change compares a new value with a positive original value using (new - original) / original x 100. Positive results are increases and negative results are decreases. A zero or negative original value is rejected because the usual percentage interpretation is undefined or can reverse the direction label.
Negative percentages
The calculator accepts negative percentages where the arithmetic is meaningful. A negative increase lowers the value, and a negative decrease raises it. Check that the sign matches the real-world situation you are modeling.
Local processing
The calculator updates in the browser as you type and does not need a server request.
FAQ
What is the formula for percent of a number?
Divide the percentage by 100, then multiply by the base value. For example, 15% of 200 is 0.15 x 200 = 30.
How is percent change calculated?
Percent change is (new value - original value) divided by the original value, multiplied by 100.
Why can the comparison value not be zero?
Percent comparisons divide by the original or whole value, so zero would make the calculation undefined. Percent-change mode also requires a positive original value to keep increase and decrease labels meaningful.
What is the difference between percent change and percent of?
Percent of finds a portion of one value, such as 15% of 200. Percent change compares two values and expresses the difference relative to the original value.
Can percentages be greater than 100?
Yes. A result above 100% can mean the part is larger than the whole, or that a new value increased by more than the original amount.
Does this handle tax, tips, or discounts automatically?
It handles the percentage math. Use the dedicated sales tax, tip, or discount calculators when you want labels and assumptions tailored to those tasks.