---
title: "Choosing measurement units"
description: "Choose and use appropriate standard units to measure length (m/cm), mass (kg/g), and capacity (litres/ml) to the nearest appropriate unit"
canonical: https://lightmysky.com/learn/mathematics/choosing-measurement-units-mt_DOe893F6gN
source: https://lightmysky.com/learn/mathematics/choosing-measurement-units-mt_DOe893F6gN.md
retrieved: 2026-10-19
---

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# Choosing measurement units

Choose and use appropriate standard units to measure length (m/cm), mass (kg/g), and capacity (litres/ml) to the nearest appropriate unit

Subject: Mathematics · Area: Measurement · Ages 6 to 7
Page: https://lightmysky.com/learn/mathematics/choosing-measurement-units-mt_DOe893F6gN

## Ready when they can

- Measure the length of a table in centimetres using a ruler
- Weigh an object in grams using a scale
- Measure the capacity of a container in millilitres using a measuring jug

## Lesson: Choosing the right unit

**Example.** Length uses centimetres (cm) or metres (m). Centimetres are convenient for short objects. Use a ruler: line up one end with zero and read the other end. Do not start at the ruler's physical edge unless zero is there. One metre is 100 centimetres.

**Example.** Mass uses grams (g) or kilograms (kg). Grams are convenient for a light object such as a grape. Use a scale, set the empty scale to zero, and check its unit. A reading of 450 on a scale set to g means 450 g. One kilogram is 1000 grams.

**Example.** Liquid volume uses millilitres (ml) or litres. Millilitres are convenient for small amounts. Use a measuring jug and read its marks at eye level. Record the number and the marked unit. One litre is 1000 ml. Litres and millilitres are volume units, not mass units.

**Example.** Metres are convenient for long lengths and tall buildings. Centimetres could describe the same length, but would give a larger number. Each metre is 100 cm. For example, 3 m is 300 cm. To change whole metres to centimetres, use 100 cm for each metre.

**Example.** Kilograms are convenient for heavier masses. A scale set to kg with a reading of 2 gives a mass of 2 kg. Read the selected unit rather than guessing it from the object. To write kilograms in grams, count 1000 g for each kilogram: 1000 g, then 2000 g for 2 kg.

**Example.** Capacity means how much a container can hold, not how much is inside now. To measure capacity with a jug, fill the container completely and measure all the liquid needed. Record the jug's unit. Litres are convenient for a large container; millilitres for a small one.

*(drawing: Choosing a convenient unit does not make other units for the same attribute invalid.)*

**Recap.** Choose a unit for the attribute and amount. Use the matching tool, read its unit, and record the number with that unit.

## Practice

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

## Needs first

- [Capacity and volume](https://lightmysky.com/learn/mathematics/capacity-and-volume-mt_4lp_b5Pzik)
- [Measuring length and height (age 5+)](https://lightmysky.com/learn/mathematics/measuring-length-and-height-age-5-mt_KaF0SQvaiu)
- [Measuring mass and weight](https://lightmysky.com/learn/mathematics/measuring-mass-and-weight-mt_zd0YkB3xNj)

## Opens up

- [Calculating with measurements](https://lightmysky.com/learn/mathematics/calculating-with-measurements-mt_6oxQPNLHNv)
- [Comparing and ordering measurements](https://lightmysky.com/learn/mathematics/comparing-and-ordering-measurements-mt_BFJ-ch_8QU)
- [Measuring length (age 7+)](https://lightmysky.com/learn/mathematics/measuring-length-age-7-mt_e4x3l2JeLI)