Converting measurement units (age 9+)
Know relative sizes of measurement units within one system (km/m/cm/mm, kg/g, l/ml, hr/min/sec); convert between different metric units and express measurements in terms of a smaller unit; record equivalents in conversion tables
What a learner can do afterwards
- Convert 3.5 km to 3,500 m
- Complete a conversion table for cm and mm: (1,10), (2,20), (3,30)...
- Express 2 kg 350 g as 2,350 g
1 · Read
You already know how to change between measurement units. Now you'll work with bigger numbers and decimals, and combine two units into one, like turning 2 kilograms 350 grams into a single number of grams.
To turn a bigger unit into a smaller one, multiply. A kilometer is 1,000 meters, so 3.5 km becomes 3.5 times 1,000, which is 3,500 m. The same rule works for kg to g and l to ml. For cm to mm, multiply by 10 instead.
A bag of flour weighs 2 kg 350 g. To write it only in grams, change the 2 kg to 2,000 g, then add the extra 350 g. 2,000 plus 350 makes 2,350 g.
Watch your zeros. Multiplying by 1,000 adds three zeros (or moves the decimal point three places right). Multiplying by 10 moves it just one place.
To change to a smaller unit, multiply by 10, 100, or 1,000, then add on any extra amount carefully.
More to read
Metric units of length review (mm, cm, m, & km)
Metric length units fit together in tens. There are 10 millimetres in 1 centimetre, 100 centimetres in 1 metre, and 1000 metres in 1 kilometre. Each step up multiplies by 10, 100, or 1000. To convert, multiply when going to a smaller unit and divide when going bigger. Kilometres to metres means times 1000, so 3.5 km is 3500 m. Metres to kilometres means divide by 1000.
Metric units of mass review (g and kg)
Mass in metric works the same tidy way. There are 1000 grams in 1 kilogram. A bag of sugar at 1 kg holds 1000 g, and a 2 kg bag holds 2000 g. Mixed masses just add the parts. 2 kg 350 g is 2000 g plus 350 g, which is 2350 g. Change the kilograms first, then add the leftover grams.
Metric units of volume review (L and mL)
Volume in metric uses litres and millilitres. There are 1000 millilitres in 1 litre. A 2 litre bottle holds 2000 mL. Small amounts suit millilitres and big amounts suit litres. Medicine cups use mL, buckets and fuel tanks use litres. Pick the unit that keeps the number friendly.
Meters and centimeters
Centimetres and millimetres pair up on every ruler. Each centimetre holds 10 millimetres, so multiply centimetres by 10 to get millimetres. A 7 cm pencil is 70 mm long. Tables of pairs show the pattern fast. 1 cm goes with 10 mm, 2 cm with 20 mm, 3 cm with 30 mm, and so on. Spot the times 10 pattern and conversions turn easy.
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2 · Watch
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Where it sits
Where this leads
18 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.