Convert between metres & centimetres
Theory
Converting between metres and centimetres is a Year 4 length skill. Because 100 cm = 1 m, you change metres to centimetres by multiplying by 100 and centimetres to metres by dividing by 100. This page explains the conversion, mixed metres-and-centimetres form, and how to compare lengths in the same unit. Changing between units of length in general comes later (Year 6 in the Australian Curriculum and in Western Australia); this page keeps to metres and centimetres used together, such as 5.25 m or 2 m 45 cm, as in Year 4. Curriculum: VC2M4M01 / AC9M4M01.
A metre (m) and a centimetre (cm) are both units for measuring length. A metre is the longer unit. There are exactly 100 centimetres in 1 metre, so \(1\text{ m} = 100\text{ cm}\).
To swap between the units you multiply or divide by 100. Changing metres to centimetres makes the number bigger, so you multiply by 100: \(9\text{ m} = 900\text{ cm}\). Changing centimetres to metres makes the number smaller, so you divide by 100: \(1100\text{ cm} = 11\text{ m}\).
Sometimes a length is written in mixed form, like \(2\text{ m }45\text{ cm}\). This means 2 whole metres plus 45 extra centimetres. Changed to a single unit it is \(200 + 45 = 245\text{ cm}\).
A length can also be written with a decimal point. \(1.5\text{ m}\) means one and a half metres. Half a metre is \(50\text{ cm}\), so \(1.5\text{ m} = 150\text{ cm}\). In the same way \(1.2\text{ m}\) is \(1\) m and \(20\) cm, which is \(120\text{ cm}\), and \(5.25\text{ m}\) is \(525\text{ cm}\). Smaller lengths use millimetres: \(10\text{ mm} = 1\text{ cm}\).
These are the facts to remember. Every conversion between metres and centimetres comes back to them.
How to convert between metres and centimetres
- Check the units. See which unit you start with and which unit you need to finish in.
- Pick the operation. Metres to centimetres, multiply by 100. Centimetres to metres, divide by 100.
- Work it out. Do the multiply or divide, then write the answer with the correct unit. For a comparison, change every length to the same unit first.
- In a problem, convert first. Change every length to centimetres, then add (joining), subtract (cutting off) or order. Change back to metres and centimetres at the end if the question asks.
| \(1\text{ m}\) | \(=\) | \(100\text{ cm}\) |
| \(15\text{ m}\) | \(=\) | \(15 \times 100\) |
| \(15\text{ m}\) | \(=\) | \(1500\text{ cm}\) |
The hose is \(1500\text{ cm}\) long.
| \(100\text{ cm}\) | \(=\) | \(1\text{ m}\) |
| \(800\text{ cm}\) | \(=\) | \(800 \div 100\) |
| \(800\text{ cm}\) | \(=\) | \(8\text{ m}\) |
The ribbon is \(8\text{ m}\) long.
| \(2\text{ m}\) | \(=\) | \(200\text{ cm}\) |
| \(200 + 35\) | \(=\) | \(235\) |
| \(2\text{ m }35\text{ cm}\) | \(=\) | \(235\text{ cm}\) |
The length is \(235\text{ cm}\).
| \(180\) | \(=\) | \(100 + 80\) |
| \(100\text{ cm}\) | \(=\) | \(1\text{ m}\) |
| \(180\text{ cm}\) | \(=\) | \(1\text{ m }80\text{ cm}\) |
The length is \(1\text{ m }80\text{ cm}\).
| \(4.5\text{ m}\) | \(=\) | \(4\text{ m} + \text{half a metre}\) |
| \(400 + 50\) | \(=\) | \(450\) |
| \(4.5\text{ m}\) | \(=\) | \(450\text{ cm}\) |
The \(.5\) means half a metre, which is \(50\) cm. The plank is \(450\text{ cm}\) long.
| \(6\text{ m}\) | \(=\) | \(600\text{ cm}\) |
| \(600 - 270\) | \(=\) | \(330\text{ cm}\) |
| \(330\text{ cm}\) | \(=\) | \(3\text{ m }30\text{ cm}\) |
Change the metres to centimetres before you subtract. \(330\) cm is left.
| \(1\text{ m }35\text{ cm}\) | \(=\) | \(135\text{ cm}\) |
| \(1\text{ m }15\text{ cm}\) | \(=\) | \(115\text{ cm}\) |
| \(135 + 65 + 115\) | \(=\) | \(315\text{ cm}\) |
| \(315\text{ cm}\) | \(=\) | \(3\text{ m }15\text{ cm}\) |
Write every part in centimetres, add, then change back. The fence is \(3\) m \(15\) cm long.
| \(1\text{ m }9\text{ cm}\) | \(=\) | \(109\text{ cm}\) |
| \(1\text{ m}\) | \(=\) | \(100\text{ cm}\) |
| \(99 < 100 < 109\) | \(<\) | \(120\) |
Shortest to longest: \(99\) cm, \(1\) m, \(1\) m \(9\) cm, \(120\) cm.
| \(9 \times 10\) | \(=\) | \(90\) |
| \(9\text{ cm}\) | \(=\) | \(90\text{ mm}\) |
| \(30 \div 10\) | \(=\) | \(3\) |
| \(30\text{ mm}\) | \(=\) | \(3\text{ cm}\) |
The same idea works with \(10\text{ mm} = 1\text{ cm}\): multiply by \(10\) to get millimetres, divide by \(10\) to get centimetres.
| \(3.7\text{ m}\) | \(=\) | \(3\text{ m }70\text{ cm} = 370\text{ cm}\) |
| \(370 - 275\) | \(=\) | \(95\) |
| \(\text{longer by}\) | \(=\) | \(95\text{ cm}\) |
The digit after the point counts tens of centimetres: \(0.7\) m is \(70\) cm. The first rope is \(95\) cm longer.
Common pitfalls
Frequently asked questions
How many centimetres are in a metre?
There are \(100\) centimetres in \(1\) metre. This is the fact you use for every conversion between metres and centimetres.
How do you convert metres to centimetres?
Multiply the number of metres by 100. For example, \(9\text{ m} = 9 \times 100 = 900\text{ cm}\).
How do you convert centimetres to metres?
Divide the number of centimetres by 100. For example, \(1200\text{ cm} = 1200 \div 100 = 12\text{ m}\).
How do you write 2 m 45 cm in centimetres?
Change the metres to centimetres first. \(2\text{ m} = 200\text{ cm}\), then add the extra \(45\text{ cm}\) to get \(245\text{ cm}\).
Which is longer, 2 metres or 180 centimetres?
Two metres is longer. Two metres is \(200\text{ cm}\), and \(200\text{ cm}\) is more than \(180\text{ cm}\).
What does 1.5 m mean in centimetres?
\(1.5\text{ m}\) is one and a half metres. One metre is \(100\text{ cm}\) and half a metre is \(50\text{ cm}\), so \(1.5\text{ m} = 150\text{ cm}\).