Identify the measured value and the uncertainty source
Determine the absolute uncertainty
Determine the relative uncertainty by dividing absolute uncertainty by the measured value
Convert relative uncertainty to percentage by multiplying by 100
For repeated measurements, calculate the mean
Find the spread of the measurements using range, standard deviation, or instrument resolution
Use half the range or standard deviation as the uncertainty when appropriate
For a single instrument reading, use the instrument’s smallest division or stated precision
For multiple quantities added or subtracted, add absolute uncertainties
For multiple quantities multiplied or divided, add relative uncertainties
For powers, multiply the relative uncertainty by the power
Report the final result with the uncertainty to the same decimal place
Write the result in the form value ± uncertainty
Include units with both the value and the uncertainty