Surface area : volume ratio
AQA GCSE Biology calculation · part of the free Calculation Climb
For a cube: surface area = 6 × side², volume = side³. The SA : V ratio shows how easily substances move in and out — smaller things have a bigger ratio.
How to do it — step by step
- Surface area of a cube = 6 × (side × side).
- Volume = side × side × side.
- Ratio = surface area ÷ volume (written as “x : 1”).
Worked example
A 2 cm cube.
SA = 6 × 2² = 24 cm². V = 2³ = 8 cm³. Ratio = 24 ÷ 8 = 3 : 1
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