# Accuracy, precision and resolution

Accuracy, precision and resolution mean different things, and datasheets often blur them. Mixing them up gives readings that look precise but are wrong.

Page: https://dharanova.com/learn/accuracy-precision-resolution · Track: Sense · Level: Foundation · Facts last checked 7 October 2026

Read first: [What a sensor actually is](https://dharanova.com/learn/what-is-a-sensor.md), [Analog-to-digital conversion](https://dharanova.com/learn/adc-basics.md)

Diagram: Four targets, centre the true value, dots the readings: a tight cluster on the centre is accurate and precise; a tight cluster off to one side is precise but not accurate; dots scattered around the centre are right on average but not precise; dots scattered off-centre are neither. A scale with fine steps shows a reading many steps away from the true value: offset, gain error and drift can be far more than one step, so high resolution does not imply high accuracy. Calibration against a known reference corrects offset and gain, cannot remove random noise, and hysteresis is hard to correct.

## Key points

1. Accuracy is closeness to the true value; precision is how closely repeated readings agree with each other (under the same conditions this is called repeatability); resolution is the smallest change the system can report. [1]
2. High resolution does not imply high accuracy: an ADC can report a reading to many digits while offset, gain error and drift make it wrong by far more than one step. [2]
3. Calibration compares readings with a known reference and uses the result to correct steady errors such as offset and gain. It cannot remove random noise, and hysteresis (a reading that depends on whether the value is rising or falling) is hard to correct. [1][2]

## Where to go next

- [Environmental sensors for VAHA: wiring, how readings reach the app, and two TVOC data-integrity gaps](https://dharanova.com/whitepapers/vaha-environmental-sensors-tvoc-data-integrity.md): a whitepaper from our lab
- [Uncalibrated bench characterisation of low-cost turbidity, TDS, pH and level sensors on Arduino Uno R4 WiFi](https://dharanova.com/whitepapers/uncalibrated-water-sensors-arduino-uno-r4-wifi.md): a whitepaper from our lab

## Sources

1. [JCGM 200:2012 International vocabulary of metrology (VIM), 3rd edition](https://www.bipm.org/documents/20126/2071204/JCGM_200_2012.pdf/f0e1ad45-d337-bbeb-53a6-15fe649d0ff1), BIPM
2. [A Basic Guide to Bridge Measurements (SBAA532A)](https://www.ti.com/lit/an/sbaa532a/sbaa532a.pdf), Texas Instruments