Sphere radius from volume calculator
Useful when you know the capacity of a spherical tank or balloon and need its size.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter volume, volume unit and length unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
r = ∛(3V / (4π)), diameter = 2r, surface area = 4πr². Liters are first converted to the chosen cubic unit.
Example
Inputs: Volume = 1,000, Volume unit = Cube of the chosen length unit, Length unit = Centimeter (cm). Result: Radius: 6.2035 cm; Diameter: 12.407 cm; Surface area: 483.5976 cm².
Limits and caveats
- Assumes a perfect sphere; real spherical tanks have wall thickness that makes the outside diameter larger.
- Results are in the chosen length unit.
Questions about this tool
How do I find a sphere radius from its volume?
Multiply the volume by 3, divide by 4π, then take the cube root. 1000 cm³ gives a radius of about 6.2 cm.
What diameter is a 1000 liter spherical tank?
Choose liters and meters, then enter 1000. The diameter is about 1.241 m.
Why does doubling the diameter give 8 times the volume?
Volume grows with the cube of the radius, and 2³ = 8.