Microscopy & measurement · SL/HL

Surface area : volume

Compare surface area and volume for simple shapes.

Your values

Number formats & units

Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.

Surface Area to Volume Ratio Calculator inputs

Calculated locally. No account or input upload.

Result & working

Example

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Formula & example

The relationship

cube:SA=6a2,V=a3\text{cube:}\quad\mathrm{SA}=6a^2,\quad V=a^3
sphere:SA=4πr2,V=43πr3\text{sphere:}\quad\mathrm{SA}=4\pi r^2,\quad V=\frac43\pi r^3
cylinder:SA=2πr2+2πrh,V=πr2h\text{cylinder:}\quad\mathrm{SA}=2\pi r^2+2\pi rh,\quad V=\pi r^2h
SA:V=SAV\mathrm{SA}:V=\frac{\mathrm{SA}}V
What the variables mean
SymbolMeaning
SA\mathrm{SA}Surface area.
VVVolume.

Worked example

Shape
Cube
Cube side length
2
Length unit
µm

SA:V = 3:1

Follow the example steps
  1. SA = 6a² = 6 × 2² = 24 µm²
  2. V = a³ = 2³ = 8 µm³
  3. SA/V = 24 / 8 = 3 µm⁻¹

Common mistakes

Surface area and volume scale with different powers of length.

Incorrect approach

L → 2L: SA/V → 2SA/V

Correct approach

SA/V = 6/L; L → 2L: SA/V → 3/L

More checks before you submit
  • Do not compare SA and V before accounting for their different dimensions.
Method notes

SA:V is a geometric comparison; biological exchange also depends on membranes, gradients, transport and metabolic demand.