First, you need to know your basic units and how they relate to each other.

Lengths
1km = 1000m
1m = 100cm
1cm = 10mm

Weights
1tonne = 1000kg
1kg = 1000g
1g = 1000mg

Capacity

1L = 1000cc
1L = 100cl
1cl = 10ml
1ml = 1cc

When you convert from a larger unit to a smaller unit you multiply
(for example, for every 1m you have 100cm, so you need to multiply by 100 to get metres in centimetres)

When you convert from a smaller unit to a larger unit you divide
(for example, for every 1000g you have 1kg, you have to divide by 1000 to get grams in kilograms)

### How to convert between units of areas

It is important to remember that areas are not units of 'cm' but 'cm2', it is no longer a length.

1m2 means a 1m by 1m square. This means a 100cm by 100cm square. So the area of this square in cm is 100cm x 100cm = 10,000cm2

For example

What is 5cm2 in mm2?

5cm2 is the same as 5 lots of 1cm2 squares (It is NOT a square that 5cm by 5cm, as that would give you a 25cm2 area!)

A 1cm2 area is given by a 1cm by 1cm square. So 1cm2 is a 1cm x 1cm square. This is the same as a 10mm x 10mm square. So the area of one such square, in millimeters squared, is 100mm2. Hence 5cm2 = 500mm2.

### How to convert between units of volume

We use the same method for converting between units of areas to converting between units of volume.

Volumes are in cm3, it has 3 dimensions!

A 10mm3 is cube with all sides 10mm (10mm x 10mm x 10mm). This means a cube with all sides 1cm (1cm x 1cm x 1cm). The volume of this cube is 1cm3.

For example

What is 3cm3 in m3?

A solid that has a volume of 3cm3, has the same volume as 3 cubes that have volumes of 1cm3.

A 1cm3 is a cube with all 3 sides of 1cm. This is the same as a cube with all 3 sides 0.01m. So the volume of one such cube, in metres cubed, is 0.01m x 0.01m x 0.01m = 0.00001m3. Hence 3cm3 = 0.00003m3.

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