Torus Volume
Enter the two radii. Results update live.
Result
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Enter numbers to see the result.
Surface area
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Tube diameter
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Formula: Volume = 2 pi^2 R r^2. Surface area = 4 pi^2 R r. Needs R > r for a ring torus.
Compute the volume of a torus (a donut shape) from the major and minor radii, plus surface area.
Enter the two radii. Results update live.
Enter numbers to see the result.
The torus volume formula comes from Pappus's centroid theorem: the volume swept by a shape equals its area times the distance its center travels. A circle of area pi r^2 whose center travels 2 pi R gives V = 2 pi^2 R r^2.
R is the distance from the center of the hole to the center of the tube; r is the tube's own radius. For a proper donut, R must exceed r. The tool warns you if the tube is fatter than the hole spacing.