Surface Area to Volume Ratio Calculator: SA/V = (4π r²)/(4/3π r³) = 3/r

Surface Area to Volume Ratio Calculator

🔬 Cells & microscopy. Use the Surface area to volume ratio (sphere) formula to find sa : v ratio, radius: pick the value you want, type the others, and the answer updates as you go.

\dfrac{SA}{V} = \dfrac{4\pi r^2}{\tfrac{4}{3}\pi r^3} = \dfrac{3}{r}

SA : V ratio (per µm)Radius (µm)

SA : V ratio0.6 per µm

Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.

What each letter means

Quantity	Unit
SA : V ratio	per µm
Radius	µm

Worked example

Find the sa : v ratio when Radius = 5 µm.

Using SA/V = (4π r²)/(4/3π r³) = 3/r: SA : V ratio = 0.6 per µm.

Frequently asked questions

What is the formula for Surface area to volume ratio (sphere)?

SA/V = (4π r²)/(4/3π r³) = 3/r.

What do the letters stand for, and what units are used?

SA : V ratio in per µm, Radius in µm.

How do you calculate sa : v ratio?

Put the values into SA/V = (4π r²)/(4/3π r³) = 3/r. For example, with Radius = 5 µm, sa : v ratio = 0.6 per µm.

Can I solve for a different value?

Yes. In the calculator above, pick the circle next to any value (sa : v ratio, radius) and fill in the others: it rearranges the formula for you.