Mass & Capacity
Learn to convert between units of mass and capacity, and compare measurements using the metric system.
Units of Mass
Mass is how heavy an object is. In Australia, we use the metric system. The main units of mass are grams (g) and kilograms (kg).
1 kilogram (kg) = 1,000 grams (g)
Everyday Examples
A letter
~20 g
An apple
~150 g
Bag of sugar
1 kg
A textbook
~500 g
Remember: To convert kilograms to grams, multiply by 1,000. To convert grams to kilograms, divide by 1,000.
Units of Capacity
Capacity is the amount of liquid a container can hold. The main units are millilitres (mL) and litres (L).
1 litre (L) = 1,000 millilitres (mL)
Common Capacities
Teaspoon
5 mL
Cup
250 mL
Water bottle
600 mL
Milk carton
1 L
Converting Between Units
Converting between units is all about multiplying or dividing by 1,000.
Bigger → Smaller (multiply)
2.5 kg = 2.5 × 1,000 = 2,500 g
3.2 L = 3.2 × 1,000 = 3,200 mL
Smaller → Bigger (divide)
4,500 g = 4,500 ÷ 1,000 = 4.5 kg
750 mL = 750 ÷ 1,000 = 0.75 L
Key Vocabulary
Mass
A measure of how heavy an object is, measured in grams or kilograms.
Capacity
The amount of liquid a container can hold, measured in millilitres or litres.
Kilogram (kg)
A unit of mass equal to 1,000 grams. About the mass of a bag of sugar.
Litre (L)
A unit of capacity equal to 1,000 millilitres. About the size of a large milk carton.
Worked Examples
Convert 3.75 kg to grams.
Step 1: We are going from a bigger unit (kg) to a smaller unit (g), so multiply.
Step 2: 3.75 × 1,000 = 3,750
Answer: 3.75 kg = 3,750 g
A recipe needs 500 mL of milk and 250 mL of cream. How many litres is that in total?
Step 1: Total in mL: 500 + 250 = 750 mL
Step 2: Convert to litres: 750 ÷ 1,000 = 0.75
Answer: Total = 0.75 L (or 750 mL)
Which is heavier: 2,300 g or 2.5 kg?
Step 1: Convert to the same unit. 2.5 kg = 2.5 × 1,000 = 2,500 g
Step 2: Compare: 2,500 g > 2,300 g
Answer: 2.5 kg is heavier.
Knowledge Check
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Key Concepts Summary
- ●1 kg = 1,000 g and 1 L = 1,000 mL.
- ●To convert from a bigger unit to a smaller unit, multiply by 1,000.
- ●To convert from a smaller unit to a bigger unit, divide by 1,000.
- ●To compare measurements, convert them to the same unit first.
- ●Use grams and millilitres for small amounts, kilograms and litres for larger ones.