Work out surface area to volume ratio instantly with clear inputs, formula shown and shareable results.
The surface-area-to-volume ratio falls as an object grows, since area scales with length² and volume with length³. For a sphere the ratio is exactly 3/r, and for a cube 6/a.
Sphere
S/V = 4πr² / (⁴⁄₃πr³) = 3/r
Cube
S/V = 6a² / a³ = 6/a
3/5 = 0.6 per unit length.
Heat loss and diffusion happen across the surface but demand scales with volume, which is why small animals lose heat faster and large cells need transport systems.