Unit Conversions

The CSSE maths paper often includes questions that involve converting between different units of length, mass, capacity, and time. You must know the key conversion facts and be confident applying them, especially in multi-step word problems.

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Length Conversions

Conversion	Fact
1 kilometre (km)	= 1,000 metres (m)
1 metre (m)	= 100 centimetres (cm)
1 centimetre (cm)	= 10 millimetres (mm)
1 metre (m)	= 1,000 millimetres (mm)

Worked Example

Convert 3.45 km to metres.

3.45 × 1,000 = 3,450 m

Worked Example

Convert 2,750 mm to metres.

2,750 ÷ 1,000 = 2.75 m

Worked Example

A piece of rope is 4.2 m long. A craftsman cuts off 85 cm. How much rope is left in centimetres?

• 4.2 m = 420 cm
• 420 - 85 = 335 cm

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Mass (Weight) Conversions

Conversion	Fact
1 kilogram (kg)	= 1,000 grams (g)
1 tonne (t)	= 1,000 kilograms (kg)

Worked Example

Convert 4.6 kg to grams.

4.6 × 1,000 = 4,600 g

Worked Example

A parcel weighs 750 g. What is this in kilograms?

750 ÷ 1,000 = 0.75 kg

Worked Example

A box of apples weighs 2.3 kg. A greengrocer has 15 boxes. What is the total weight in kg?

2.3 × 15 = 34.5 kg

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Capacity (Volume) Conversions

Conversion	Fact
1 litre (l)	= 1,000 millilitres (ml)
1 centilitre (cl)	= 10 millilitres (ml)
1 litre (l)	= 100 centilitres (cl)

Worked Example

A jug holds 1.5 litres. How many millilitres is that?

1.5 × 1,000 = 1,500 ml

Worked Example

Each glass holds 250 ml. How many glasses can be filled from a 2-litre bottle?

• 2 litres = 2,000 ml
• 2,000 ÷ 250 = 8 glasses

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Time Conversions

Conversion	Fact
1 minute	= 60 seconds
1 hour	= 60 minutes
1 day	= 24 hours
1 week	= 7 days
1 year	= 365 days (366 in a leap year)

Converting between 12-hour and 24-hour clock