To understand centimetres and millimetres it is first helpful to think of them in relation to a metre.
Do you think that a millimetre is bigger or smaller than a centimetre?
A millimetre is smaller than a centimetre.
Milli meaning one thousandth, so the word millimetre means one thousandth of a metre.
A millimetre is a thousand times smaller than a metre.
Millimetre can be written as mm.
1000mm = 1m
How many mm are there in every cm?
There are 10mm in every 1cm.
Millimetres can be written using the unit mm or as parts of a centimetre.
So, to convert between mm and cm have a look at this handy diagram.
When converting from cm to mm you must multiply by 10.
When converting from mm to cm you must divide by 10.
10mm =
1cm
÷ 10
x 10
If something measures 5mm what would this be in cm?
If a pea measures 8mm what would this be in cm?
5 divided by 10 = 0.5
So a measurement of 5mm could be converted to 0.5cm
8 ÷ 10 = 0.8
8mm = 0.8cm
Let’s practise.
Write these mm measurements as cm.
2mm = 0.2cm
7mm = 0.7cm
9mm = 0.9cm
15mm = 1.5cm
43mm = 4.3cm
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If something measures 2cm what would this be in mm?
If a marble measures 3cm what would this be in mm?
2 multiplied by 10 = 20
So a measurement of 2cm could be converted to 20mm.
3 x 10 = 30
3cm = 30mm
Write these cm measurements as mm.
0.3cm = 3mm
12cm = 120mm
6cm = 60mm
45cm = 450mm
17cm = 170mm
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Answer true or false for each of these statements.
When you convert from mm to cm you divide by 10. True
4cm is the same as 0.4mm. False
When you convert from cm to mm you multiply by 10. True
12mm is the same as 1.2cm. True
35mm is the same as 350cm. False
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Let’s play a quick quiz!
For each question there will be four options. Click on the correct answer.
Convert 67mm to cm.
67cm
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Back
6.7cm
670cm
0.67cm
How many mm are there in 20cm?
200
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Back
2000
20
0.2
Convert 78cm into mm.
7.8mm
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Back
78mm
0.78mm
780mm
Convert 565mm into cm
56cm
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5.65cm
56.5cm
0.565cm
Select the measurement that is larger.
673mm
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7.55cm