A familiar situation
Work out a circular table’s circumference or surface area from its diameter.
How to use this calculator
- Enter known measurement, measurement.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How circle is calculated
The circle relations are d=2r, circumference=2πr, and area=πr². If circumference or area is entered, radius is recovered before the other values are calculated. A circle with diameter 10 cm has circumference 10π ≈ 31.416 cm and area 25π ≈ 78.540 cm².
d=2r; circumference=2πr; area=πr².A circle with diameter 10 cm has circumference 10π ≈ 31.416 cm and area 25π ≈ 78.540 cm².
Assumptions & useful context
The result depends on the values you enter and the method described above. Displayed numbers may be rounded; calculations use the unrounded values. Check that this model matches your situation before relying on it.
Frequently asked questions
May a circumference or area be zero?
No; a zero-size circle has no positive radius.
Why is area in squared units while circumference is in ordinary units?
Area spans two dimensions; circumference measures a length around the boundary.