Topics / Maths
3D shapes: volume and surface area
Volume is how much space a 3D shape takes up; surface area is the total area of all its faces. For a cuboid (a box shape) both come from just three measurements: length, width and height.
What is tested
- Volume of a cuboid: length × width × height
- Surface area: adding the areas of all six faces
- Counting cubes, and converting cm³ to litres (1,000 cm³ = 1 litre)
Worked example
A box measures 5 cm by 4 cm by 3 cm. Find its volume and its surface area.
- Volume = 5 × 4 × 3 = 60 cm³.
- The faces come in three matching pairs: 5 × 4 = 20, 5 × 3 = 15 and 4 × 3 = 12 cm².
- One of each pair: 20 + 15 + 12 = 47 cm².
- Double it for all six faces: 47 × 2 = 94 cm².
Answer: Volume 60 cm³; surface area 94 cm²
Exam-day checklist
- Volume uses cubic units (cm³); area uses square units (cm²).
- A cuboid has 6 faces in 3 matching pairs.
- Make sure all lengths are in the same unit first.
- 1,000 cm³ = 1 litre.
Common mistakes
- Adding the three lengths instead of multiplying.
- Counting only three faces for surface area.
- Mixing cm and m in one calculation.
Try it yourself
1. How many 1 cm cubes fill a box 6 cm long, 2 cm wide and 3 cm high?
Show answer
36
6 × 2 × 3 = 36 cubes.
2. A fish tank is 50 cm long, 20 cm wide and 10 cm high. How many litres does it hold when full?
Show answer
10 litres
50 × 20 × 10 = 10,000 cm³, and 1,000 cm³ = 1 litre.
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