---
title: "Converting units with decimal notation"
description: "Convert among different-sized standard measurement units within a given system (e.g. 5 cm to 0.05 m) using decimal notation to up to three decimal places; convert between smaller and larger units of l"
canonical: https://lightmysky.com/learn/mathematics/converting-units-with-decimal-notation-mt_2VpdPjvewx
source: https://lightmysky.com/learn/mathematics/converting-units-with-decimal-notation-mt_2VpdPjvewx.md
retrieved: 2026-09-02
---

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# Converting units with decimal notation

Convert among different-sized standard measurement units within a given system (e.g. 5 cm to 0.05 m) using decimal notation to up to three decimal places; convert between smaller and larger units of length, mass, volume, and time

Subject: Mathematics · Area: Measurement · Ages 10 to 11
Page: https://lightmysky.com/learn/mathematics/converting-units-with-decimal-notation-mt_2VpdPjvewx

## Ready when they can

- Convert 3,250 g to 3.25 kg using decimal notation
- Convert 0.45 km to 450 m
- Explain the relationship between mm, cm, m, and km using powers of 10

## Lesson: Writing conversions as decimals

You already know how to change centimeters to meters or grams to kilograms. Now you will write those changes using decimal points, like 3.25 kg instead of 3 kg and 250 g separately.

*(drawing: Each unit on the ladder is a power of 10 bigger than the one before it.)*

The metric units climb in powers of 10. Ten millimeters make a centimeter, a hundred centimeters make a meter, and a thousand meters make a kilometer. Going from a small unit to a big one, you divide by that number. Going from a big unit to a small one, you multiply. The digits stay the same, and only the decimal point moves.

**Example.** Mia has 3,250 g of flour. Since 1,000 g makes 1 kg, she divides by 1,000: 3,250 divided by 1,000 is 3.25. So she has 3.25 kg of flour.

**Example.** A race is 0.45 km long. Since 1 km makes 1,000 m, multiply by 1,000: 0.45 times 1,000 is 450. The race is 450 m long.

**Tip.** Sanity-check the size of your answer. The same distance is a smaller number in kilometers than in meters, so if your number grew when the unit got bigger, the decimal point moved the wrong way.

**Recap.** Multiply or divide by 10, 100, or 1,000 to change units, and write the exact answer with a decimal point.

## Practice

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

## Needs first

- [Multiplying and dividing (age 10+)](https://lightmysky.com/learn/mathematics/multiplying-and-dividing-age-10-mt_wPgpMJ0-PA)
- [Converting measurement units (age 9+)](https://lightmysky.com/learn/mathematics/converting-measurement-units-age-9-mt_Zks8xyInSG)

## Opens up

- [Measurement Conversions](https://lightmysky.com/learn/mathematics/measurement-conversions-mt_SqhXQhAEUf)
- [Unit Conversions](https://lightmysky.com/learn/mathematics/unit-conversions-mt_tpT9brpI6D)