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Frustum Volume Calculator
Calculate the volume of a conical frustum (a cone with the top sliced off) from its two radii and height.
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What this calculator finds
A frustum is what remains of a cone (or pyramid) after slicing off the top with a cut parallel to the base. This calculator finds the volume of a conical frustum, plus its slant height and lateral surface area.
The formula
Volume is V = (πh/3)(r1² + r2² + r1·r2), where r1 is the top radius, r2 is the bottom radius, and h is the vertical height between them. The slant height is found with l = √(h² + (r2 – r1)²), and lateral surface area is π(r1 + r2)l.
This shape shows up in buckets, lampshades, and traffic cones. This tool is for general math and design estimation purposes.
Last reviewed August 2026