How it’s calculated
A sphere is every point at distance r from a centre.
Example: r = 3 in gives V = (4/3) × π × 27 = 36π ≈ 113.10 in³ and SA = 4 × π × 9 = 36π ≈ 113.10 in² (numerically equal only at r = 3).
Frequently asked questions
What is the volume formula for a sphere?
V = (4/3)πr³. Doubling the radius makes the volume eight times larger.
How do I find the radius of a ball I can’t cut open?
Wrap a tape around its widest part to get the circumference, choose “Circumference”, and the calculator finds r = C ÷ 2π.
How do I get a hemisphere?
Halve the volume. The curved surface of a hemisphere is 2πr², plus πr² if you include the flat base.
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Sources
- Prealgebra 2e, 9.6 Solve Geometry Applications: Volume and Surface Area — OpenStax
- Sphere — Wolfram MathWorld
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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