Convert between metric units of length - mm, cm, m
Theory
There are 10 mm in a centimetre and 100 cm in a metre. To change to a smaller unit, multiply; to change to a larger unit, divide.
Length can be measured in millimetres (mm), centimetres (cm) or metres (m).
The units are linked: \(1\text{ cm} = 10\text{ mm}\), \(1\text{ m} = 100\text{ cm}\), and so \(1\text{ m} = 1000\text{ mm}\).
Changing to a smaller unit gives a bigger number, so multiply. Changing to a larger unit gives a smaller number, so divide.
Use the right factor for each pair of units.
| Change | Do this |
|---|---|
| cm to mm | \(\times 10\) |
| mm to cm | \(\div 10\) |
| m to cm | \(\times 100\) |
| cm to m | \(\div 100\) |
How to convert a length
- Decide whether the new unit is smaller or larger.
- Choose the factor: \(10\) between mm and cm, \(100\) between cm and m.
- Multiply for a smaller unit, or divide for a larger unit.
Smaller unit, so multiply by \(10\): \(5 \times 10 = 50\).
The answer is 50 mm.
Larger unit, so divide by \(10\): \(35 \div 10 = 3.5\).
The answer is 3.5 cm.
Smaller unit, and \(1\text{ m} = 1000\text{ mm}\): \(0.6 \times 1000 = 600\).
The answer is 600 mm.
Smaller unit, so multiply by \(100\): \(2 \times 100 = 200\).
The answer is 200 cm.
Common pitfalls
Frequently asked questions
How many millimetres are in a centimetre?
There are \(10\) millimetres in \(1\) centimetre.
How do you change centimetres to millimetres?
Multiply by \(10\), because millimetres are the smaller unit. For example \(5\text{ cm} = 50\text{ mm}\).
How do you change millimetres to centimetres?
Divide by \(10\), because centimetres are the larger unit. For example \(35\text{ mm} = 3.5\text{ cm}\).
How many millimetres are in a metre?
There are \(1000\) millimetres in \(1\) metre, because \(10 \times 100 = 1000\).