Converting metric units: what children learn
In this game children match measurements to the same amount in another unit, such as 2.5 km to 2,500 m or 0.25 kg to 250 g. The measurements include decimals, so children also practice multiplying and dividing decimals by 10, 100 and 1,000.
Supports part of Common Core 5.MD.A.1: converting measurement units within the metric system. This focused game does not cover the entire standard.
Common Core connection: 5.MD.A.1. This is focused practice for part of the standard.
How to play
Pick a card on the left, then the card on the right that matches it. Each game has 6 pairs. Wrong matches are counted as mistakes, and you get three stars for a game with no mistakes.
Step by step
- Know the key facts. 1 km = 1,000 m, 1 m = 100 cm, 1 cm = 10 mm, 1 kg = 1,000 g and 1 liter = 1,000 ml.
- Big unit to small: multiply. Going from a bigger unit to a smaller one, the number gets bigger. 3 km is 3 × 1,000 = 3,000 m.
- Small unit to big: divide. Going from a smaller unit to a bigger one, the number gets smaller. 750 ml is 750 ÷ 1,000 = 0.75 liters.
- Move the digits. Multiplying by 1,000 moves each digit three places to the left: 1.75 km becomes 1,750 m.
Worked examples
Example 1: Convert 4 m to centimeters.
Working: 1 m = 100 cm, so 4 × 100.
Answer: 400 cm
Example 2: Convert 0.25 kg to grams.
Working: 1 kg = 1,000 g, so 0.25 × 1,000.
Answer: 250 g
Example 3: Convert 65 mm to centimeters.
Working: 10 mm = 1 cm, so 65 ÷ 10.
Answer: 6.5 cm
Common mistakes and how to fix them
- Using 100 for every conversion. Only meters and centimeters use 100. Kilo- means 1,000 and milli- means one thousandth.
- Multiplying when going to a bigger unit. Ask: will there be more or fewer of the new unit? Fewer big units means divide.
- Writing 1.5 kg as 1,050 g. 0.5 kg is half a kilogram, which is 500 g, so 1.5 kg is 1,500 g.
Activities to try at home
- Read food labels and convert: is a 1.5 liter bottle more than 1,200 ml?
- Measure a room in meters and centimeters, then write it in centimeters only.
- Look at road signs and running distances in kilometers and convert them to meters.
Ideas for the classroom
- Make a conversion washing line from mm to km.
- Students measure objects in one unit and convert to another.
- Solve recipe problems that use g, kg, ml and liters.
Free printable game and worksheet
The free printable starts with a game sheet, such as a color-by-answer picture, an answer maze or a secret-code joke, followed by a worksheet. Both use the same checked questions as the online game, and the answers are on the last page. Print it, or save it as a PDF from your browser’s print menu.
Open the free printable game and worksheet
Frequently asked questions
How should I choose this game for my learner?
Supports part of Common Core 5.MD.A.1: converting measurement units within the metric system. This focused game does not cover the entire standard.
Why does the game use commas in 1,000?
Commas separate thousands and make large numbers easier to read, as in most UK textbooks.
Can it be played with a keyboard?
Yes. Tab to a card, press Enter to pick it, then pick its partner.