3D shapes
Capacity and volume
In this unit you learn the difference between capacity and volume, how to read a measuring scale, and how to change between millilitres and litres. Remember: 1 litre = 1000 ml.
Capacity and volume
Capacity is the maximum amount a container can hold. Volume is the amount of liquid that is actually in the container right now. They are only the same number when the container is full. Usually the volume is less than the capacity.
Reading a scale
On a measuring jug, the capacity is the highest mark on the scale. The volume is the mark the liquid reaches. Read the scale carefully — count the size of each step first.
Millilitres and litres
1 litre = 1000 ml. So 2500 ml = 2 litres 500 ml = 2.5 litres. To change ml to litres, split off each 1000 ml as 1 litre; the rest becomes the decimal part.
Filling to capacity and fractions of a container
To find how much more liquid fills a container, subtract: capacity − volume. To find a fraction of a container that is full, work out that fraction of the capacity. For example, half of 120 litres is 60 litres.
Worked examples
Capacity and volume from a jug
- The jug can hold up to the 600 ml mark, so its capacity is 600 ml.
- The water reaches the 500 ml mark.
- So the volume of water is 500 ml.
Answer: Capacity = 600 ml and volume of water = 500 ml.
How much more to fill it
- The capacity is 600 ml and the volume of water is 500 ml.
- Subtract to find how much more is needed: 600 − 500.
Answer: 600 − 500 = 100 ml more is needed to fill the jug.
Changing millilitres to litres
- Change 2500 ml to litres, using 1 litre = 1000 ml.
- 2500 ml = 2000 ml + 500 ml = 2 litres 500 ml.
- 500 ml is 0.5 of a litre.
Answer: 2500 ml = 2 litres 500 ml = 2.5 litres.
A fraction of the capacity
- A fish tank has a capacity of 120 litres and is half full.
- Work out half of the capacity: half of 120 litres.
Answer: Half of 120 litres is 60 litres of water.
Where you see this in real life
- Measuring the correct amount of milk in a jug to make pancakes.
- Filling a fish tank part-way and working out the volume of water.
- Reading how much juice is in a bottle marked with its capacity.
Key words
- Capacity
- The maximum amount a container can hold.
- Volume
- The amount of liquid that is actually in a container.
- Millilitre (ml)
- A small unit for measuring liquid. 1000 ml = 1 litre.
- Litre
- A unit for measuring liquid. 1 litre = 1000 ml.