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Sphere Radius Calculator

By Sphere Volume Formula Editorial Team Published on September 25, 2026 Peer-Reviewed • SI & Imperial Units

Sphere Radius Calculator (Reverse Geometry)

Determine the exact radius of a sphere when only the total volume or surface area is known by applying inverse algebra: r = ³√(3V / 4π) or r = √(A / 4π).

Inverse Radius Formulas
From Volume: r = ³√[ (3 × V) / (4 × π) ]
From Surface Area: r = √[ A / (4 × π) ]

Step-by-Step Inversion

  1. Multiply volume V by 3.
  2. Divide by 4π (≈ 12.56637).
  3. Take the cube root of the quotient.

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