---
title: "Measuring with different units"
description: "Measure the length of an object using two different length units and describe how the measurements relate to the size of the unit chosen"
canonical: https://lightmysky.com/learn/mathematics/measuring-with-different-units-mt_jHv4BgRK8B
source: https://lightmysky.com/learn/mathematics/measuring-with-different-units-mt_jHv4BgRK8B.md
retrieved: 2026-10-19
---

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# Measuring with different units

Measure the length of an object using two different length units and describe how the measurements relate to the size of the unit chosen

Subject: Mathematics · Area: Measurement · Ages 7 to 8
Page: https://lightmysky.com/learn/mathematics/measuring-with-different-units-mt_jHv4BgRK8B

## Ready when they can

- Measure a desk in both centimetres and inches and compare the two numbers
- Explain that measuring with a smaller unit gives a larger number
- Predict whether a measurement in centimetres will be greater or less than in inches

## Lesson: Measuring with different units

You already know how to measure things with a ruler. Did you know you can measure the very same object with two different units? The numbers you get will not match, even though the object stays exactly the same size.

*(drawing: The same book measured two ways: 20 centimetres, or 8 inches.)*

**Example.** Mia measures her desk with a centimetre ruler and counts to 100. Then she measures the same desk with an inch ruler and only counts to 39. The desk did not change size. Inches are a bigger unit, so she needed fewer of them.

**Tip.** Here is the rule: a smaller unit needs more copies to cover the same length, so it gives a bigger number. A bigger unit needs fewer copies, so it gives a smaller number.

**Recap.** Same object, different units: the smaller the unit, the bigger the number you count.

## Practice

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

## Needs first

- [Measuring length (age 7+)](https://lightmysky.com/learn/mathematics/measuring-length-age-7-mt_e4x3l2JeLI)

## Opens up

- [Converting measurement units](https://lightmysky.com/learn/mathematics/converting-measurement-units-mt_d8al9JcajP)