Accuracy
The closeness of a measured value to the true or accepted value of the quantity being measured.
Formula / equation
% error = |measured − true| / true × 100
Unit
Dimensionless
In depth
Accuracy is degraded by systematic error — a miscalibrated balance, an uncorrected meniscus reading, or an incompletely dried sample — which shifts every result in the same direction. Systematic error cannot be reduced by repeating the measurement; it is removed by calibration against a standard.
Examples in the real world
A balance reading 10.02 g for a certified 10.00 g mass is accurate to 0.2%; one reading 10.50 g is precise but inaccurate.