Percentage Calculator
Free to use, with no sign up. Your entries stay in this browser; calculations run on your device.
Result
X% of Y = (X / 100) × Y, in the same units as Y. X is what % of Y = (X / Y) × 100%. Change from X to Y = ((Y − X) / |X|) × 100%.
NIST SP 811, section 7.10.2 defines % as 0.01. The U.S. Bureau of Labor Statistics documents the percent-change formula.
Worked example: 20% of 150 = 30 units. 30 is 20% of 150. A change from 80 to 100 = (100 − 80) / 80 × 100 = 25%.
Use the same units for the part and whole or the original and new values. Zero denominators are undefined. A negative original value is divided by its size, so a fall always shows as a negative change; the result is not a financial interpretation. Values are limited to ±1 trillion; display rounding does not change the underlying calculation.
How to use this tool
Choose one of the three percentage operations. Enter X and Y in matching units where appropriate, then select Calculate. The formula for each operation appears below.
Frequently asked questions
Can I enter negative numbers?
Yes. Percentage change divides by the size of the original value, so a fall is always negative and a rise is always positive, even when the original value is negative: from −80 to −100 is −25%.
Why can zero give an error?
Calculating a part as a percentage of a zero whole or a change from a zero original value requires division by zero. Those percentages are undefined. Zero percent of a number is valid.
Is percentage change the same as percentage-point change?
No. From 20% to 30% is an increase of 10 percentage points, but the relative percentage change is (30 − 20) / 20 × 100 = 50%.