Frustum of a cone volume calculator
A frustum is a cone with its top cut off, like a bucket, a cup or a flower pot.
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How to use it
- Enter bottom (large) radius, top (small) radius, height and length unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Volume = πh/3 × (R² + Rr + r²), slant s = √(h² + (R − r)²), lateral area = π(R + r)s, total = lateral + πR² + πr².
Example
Inputs: Bottom (large) radius = 4, Top (small) radius = 2, Height = 3, Length unit = Centimeter (cm). Result: Volume: 87.9646 cm³; Slant height: 3.6056 cm; Lateral surface area: 67.963 cm².
Limits and caveats
- Covers right circular frustums with parallel top and bottom.
- Results are in the cube or square of the unit you chose, so enter every dimension in that same unit.
Questions about this tool
How do I find the capacity of a bucket?
Measure the inside diameter at the top and bottom and the depth, then enter half of each diameter and the depth. Liters appear directly.
What if both radii are equal?
The shape becomes a cylinder and the formula gives the cylinder volume πr²h.
Does it matter which radius is larger?
No. The formula is symmetric, so either radius can go in either field.