Radius of a Sphere Calculator
Calculate every dimension of a sphere from any one known value. Enter the radius to get volume, surface area and circumference — or work backwards from a known volume or surface area to find the radius.
Solve from
units
Radius of the sphere in the same units as your input
r = 5
- 1
Volume = (4/3) × π × r³
(4/3) × π × 5³ = 523.5988 - 2
Surface area = 4 × π × r²
4 × π × 5² = 314.1593
How does this calculator work?
A sphere with radius r has volume V = (4/3)πr³ and surface area SA = 4πr². Enter any one — radius, volume or surface area — and the calculator instantly returns all other dimensions. Reverse formulas: r = ∛(3V/4π) from volume, r = √(SA/4π) from surface area.
Formula
How this is calculated
A sphere is the set of all points in 3-D space at exactly one distance — the radius r — from a centre point. Two formulas govern its size: the volume V = (4/3)πr³ and the surface area SA = 4πr². Both follow from integrating over the spherical surface, and knowing any one quantity determines all the others by rearranging these equations.
To find the radius from a known volume, rearrange to r = ∛(3V / 4π). To find it from a known surface area, rearrange to r = √(SA / 4π). The diameter is simply 2r, and the great-circle circumference — the perimeter of the largest cross-section — is 2πr, identical to the circumference of a circle of the same radius.
All results share the same linear unit: if you enter radius in centimetres, volume is in cm³ and surface area in cm². No unit conversion is performed — keep your inputs consistent.
Frequently asked questions
Rearrange V = (4/3)πr³ to r = ∛(3V / 4π). Choose "Volume" in the calculator, enter the value, and the radius is shown instantly along with surface area, diameter and circumference.
From SA = 4πr², rearranging gives r = √(SA / 4π). Choose "Surface area" as the input mode, enter the value, and all other dimensions are derived automatically.
The radius is the distance from the centre to the surface; the diameter spans the sphere through the centre and equals exactly twice the radius (d = 2r). The great-circle circumference is πd = 2πr.
Also known as
TG we-Calculate Editorial Team. (2026). Radius of a Sphere Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/radius-of-sphere-calculator
TG we-Calculate Editorial Team. "Radius of a Sphere Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/radius-of-sphere-calculator.
TG we-Calculate Editorial Team, "Radius of a Sphere Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/radius-of-sphere-calculator
@misc{wecalculate_radius_of_sphere_calculator, title = {Radius of a Sphere Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/radius-of-sphere-calculator}}, year = {2026}, note = {TG we-Calculate} }
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