Use our calculator below to quickly find percentage uncertainty for your science labs, physics experiments, and data reporting. Just enter the measured value and its uncertainty, and the calculator will instantly display the percentage uncertainty—making your work faster, easier, and more accurate.

What is Percentage Uncertainty?

Percentage uncertainty is a way of showing how accurate a measurement is compared to the size of the measurement itself.

It tells you how much “doubt” there is in your result, expressed as a percentage.

You calculate it by dividing the uncertainty (the possible error in the measurement) by the measured value, and then multiplying by 100:

Percentage Uncertainty= (Uncertainty/Measured Value)×100

For example, if you measure a stick and get 80 cm ± 2 cm, the uncertainty is 2 cm. The percentage uncertainty is: 2/80×100=2.5%

This means your measurement could be off by about 2.5%, giving you a clear idea of how reliable the number is.