Units of measure

• Length: 10 mm = 1 cm, 100 cm = 1 m, 1000 m = 1 km.
• Mass: 1000 g = 1 kg. Capacity: 1000 ml = 1 l.
• Area: 1 cm² = 100 mm², 1 m² = 10 000 cm², 1 km² = 1 000 000 m².
• Volume: 1 cm³ = 1000 mm³, 1 m³ = 1 000 000 cm³.
• Volume and capacity: 1 cm³ = 1 ml, 1000 cm³ = 1 l, 1 m³ = 1000 l.
• Convert to one unit before adding, comparing or dividing in a practical problem.

Multiply to a smaller unit, divide to a larger one

Going to a smaller unit gives a bigger number, so multiply. Going to a larger unit, divide.

Square the length factor

A square 1 m by 1 m is also 100 cm by 100 cm, so it contains 100 × 100 = 10 000 cm².

Cube the length factor; 1 cm³ = 1 ml

A cube 1 m on each side is 100 cm on each side, so it contains 100³ = 1 000 000 cm³. Capacity is the volume a container holds, measured in ml and l.

Change to one unit first

Before you divide one quantity by another, put them in the same unit. Then check the answer is sensible: a room does not need 1.4 tiles or 14 000 tiles.