Percent Error Calculator

Percent error equals the absolute value of (experimental minus theoretical), divided by the absolute value of the theoretical, times 100. For 9.8 against 9.81 that is 0.01 / 9.81 x 100, about 0.101937%.

Percent difference is the absolute difference of two values divided by their mean magnitude, times 100: |a - b| / ((|a| + |b|) / 2) x 100. It is symmetric, so swapping the two values gives the same answer.

Use percent error when one value is a known, accepted, or expected reference and the other is your measurement. Use percent difference when you compare two measurements and neither is treated as correct.

Percent error divides by the accepted value, and dividing by zero is undefined. The engine throws an error rather than returning infinity when the theoretical value is zero.

The mean magnitude becomes zero, so percent difference is undefined. The tool reports an error in that case instead of a nonsensical number.

Yes. If the measurement is far from the accepted value, the error easily exceeds 100 percent. For example 5 against an accepted 2 gives 150 percent.

No. Both formulas take an absolute value, so the result is always zero or positive. A perfect match with the accepted value gives exactly 0 percent.

The display keeps up to six significant figures and trims trailing zeros, so a clean 2% shows as 2% while a long decimal like 0.1019367... shows as 0.101937%.

Yes. Every calculation runs locally in your browser, so nothing you type is uploaded or stored.