Primary 5 Maths: Volume

Updated Sept 2026

Volume of cubes and cuboids, counting unit cubes, cm³/ℓ/mℓ conversions, and water-level tank problems — worked P5 examples aligned to the MOE syllabus.

Most schools typically cover this topic in Term 4, around weeks 1–3 — though every school sets its own sequence.

Volume is Primary 5's first proper 3-D measurement topic. It starts simply — a cuboid built from unit cubes — and quickly becomes a unit-conversion topic in disguise, because most real questions ask for an answer in litres or millilitres while the working happens in cm³. MOE's 2021 Primary Mathematics Syllabus places cubes, cuboids and this conversion work at Primary 5, with volume of other solids (like cylinders and prisms) left for Primary 6.

Two formulas cover almost every question: Volume of a cuboid = length × breadth × height, and Volume of a cube = side × side × side (a cube is just a cuboid where all three measurements are equal). The one conversion fact that unlocks the water-tank questions: 1000 cm³ = 1 litre, and so 1 cm³ = 1 mℓ.

P5 Volume: the mistakes to watch for

• Mixing up cm³ and cm² for volume. Volume needs three dimensions multiplied together; a question that only gives two measurements is asking for area, not volume — check that all three of length, breadth and height are actually given or found first.
• Forgetting to convert before comparing or adding. A question that mixes litres and cm³ in the same sentence has to be converted to one unit before any arithmetic happens — usually cm³, since that's what the multiplication produces.
• Treating "rise in water level" as the tank's new water volume. When a solid object is lowered into a tank, the volume of water that rises equals the volume of the object — not the volume of all the water now in the tank.
• Assuming a cube's edge is easy to spot from its volume. Finding the edge of a cube from its volume means asking "what number, multiplied by itself three times, gives this volume?" — a step children often skip and guess instead.

P5 Volume: cuboids, cubes and the litre conversion

P5 Volume: cuboids, cubes and unit cubes

P5 Volume: exam-style unit cubes and missing dimensions

PSLE challenge: water-level and multi-step volume problems

How to practise this topic

Write "cm³" or "ℓ" next to every number as it's read out of a question — most volume mistakes are unit mistakes, not multiplication mistakes. For water-level questions, sketch the tank as a side-on rectangle and shade the rise, exactly as in the diagram above, before deciding what to multiply. Volume questions often lean on fraction and decimal working from earlier topics, so P5 Decimals is a good companion topic if the conversion arithmetic itself feels shaky, and the multi-step reasoning above is the same style tested throughout P5 Word Problems.

What this topic covers

In the MOE Primary Mathematics syllabus, Primary 5 Volume includes the concepts below. (P5-M-10 is Test Paper's own topic code, not an MOE reference.)

• Volume of a cube
• Volume of a cuboid
• Finding edge/length given volume
• Volume word problems

Before this topic

These topics feed into Volume — if this one wobbles, check them first: Primary 5 Area & Perimeter · Primary 5 Whole Numbers (up to 10 million).

Where to go next

• Other Primary 5 topics: Primary 5 Fractions · Primary 5 Decimals · Primary 5 Percentage
• All Primary 5 Maths topics, or every P4–P6 topic
• Not sure this is the weak topic? How to find which Maths topics your child is weak in