---
title: "Precision, accuracy and significant figures"
description: "Distinguish between precision (consistency of repeated readings) and accuracy (closeness to true value), use significant figures and standard form correctly, and choose and use appropriate measuring i"
canonical: https://lightmysky.com/learn/science/precision-accuracy-and-significant-figures-mt_auJqTemMpI
source: https://lightmysky.com/learn/science/precision-accuracy-and-significant-figures-mt_auJqTemMpI.md
retrieved: 2026-09-12
---

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# Precision, accuracy and significant figures

Distinguish between precision (consistency of repeated readings) and accuracy (closeness to true value), use significant figures and standard form correctly, and choose and use appropriate measuring instruments to minimise uncertainty

Subject: Science · Area: Scientific Inquiry · Ages 11 to 12
Page: https://lightmysky.com/learn/science/precision-accuracy-and-significant-figures-mt_auJqTemMpI

## Ready when they can

- Explains the distinction between precision and accuracy with examples
- Rounds measurements to an appropriate number of significant figures
- Selects a measuring instrument with appropriate resolution for the context (e.g. choosing a 10 ml measuring cylinder rather than a 1-litre measuring jug for a 5 ml measurement)

## Lesson: Precision and accuracy: why repeats aren't everything

When you measure something several times, two different questions matter. Do your readings agree with each other? And do they match the true value? The first question is about precision. The second is about accuracy.

*(drawing: Five weighings of the same stone: 20.1g, 20.2g, 20.1g, 20.2g, 20.1g. They agree closely, but the true mass is 19.0g.)*

**Example.** Priya measures a pencil three times with a ruler and gets 15.2 cm, 15.2 cm, and 15.3 cm. Her readings agree closely, so they are precise. If the pencil's real length is about 15.2 cm, she is also accurate. But if her ruler had a bent end and the real length was 14.0 cm, her readings would still be precise. They would just be precise and wrong.

**Tip.** Pick an instrument that matches the size of what you are measuring. A 10 ml cylinder lets you read a 5 ml sample far more precisely than a 1 litre jug would. When you write down a result, only use as many significant figures as your instrument can actually support. Extra digits don't make a measurement more true.

**Recap.** Precision means repeats agree with each other, accuracy means they agree with the true value, and more repeats alone can't fix a badly calibrated instrument.

## Practice

17 questions on this page, each with its working shown.

## Needs first

- [Accurate Measurement](https://lightmysky.com/learn/science/accurate-measurement-mt_Psun-u_lPf)

## Opens up

- [Tables, charts, and graphs](https://lightmysky.com/learn/science/tables-charts-and-graphs-mt_YHsUhi4Prc)