Home / Topics / Measurement & Math Tools
Accuracy vs precision
Beginner
Accuracy is closeness to truth; precision is repeatability.
Accuracy is how close a result is to the true value. Precision is how close repeated results are to each other. A scale that always reads 0.5 kg too high is precise but not accurate, and a scale that scatters around the correct value is accurate on average but not precise.
Darts all clustered in the top left of the board: precise, not accurate. Darts scattered evenly around the bullseye: accurate on average, not precise.
Averaging many readings improves precision but cannot remove a systematic offset.
In more detail
Accuracy is how close a measurement is to the true value, while precision is how well repeated measurements agree. A measurement can be precise but not accurate if the instrument has a systematic offset.
Real-world uses
- A balance that always reads 1 g too high is precise but not accurate, and it needs calibration.
- Quality control in manufacturing checks both accuracy and precision of measuring equipment.
- A sniper zero on a rifle must be both accurate, hitting the right point on average, and precise, grouping shots tightly.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
Can a result be accurate but not precise?
Yes, if the average of several noisy readings is close to the true value but the individual readings scatter widely.
Which matters more?
It depends on the task. Accuracy matters for matching a known standard; precision matters for detecting small changes.
Can I improve precision by taking more readings?
Yes, averaging more readings reduces random scatter, but it does not correct an accuracy problem caused by a faulty instrument.
Related topics in Measurement & Math Tools
Mass vs weight · Significant figures · Rounding rules · Systematic error · Random error · Absolute error