Circumference Calculator
Circumference is the distance around a circle — what you need for fencing a round garden, sizing a ring road or wrapping a pipe. Enter the radius, diameter or area and get the circumference plus every other measurement.
Results
Formula
How to use this calculator
- Choose the measurement you have: radius, diameter or area.
- Enter the value.
- Press Calculate for the circumference and the remaining measures.
Worked example
A round table with diameter 10.
- Circumference: π × 10 ≈ 31.416.
- Radius: 10 ÷ 2 = 5; area: π × 25 ≈ 78.54.
Result: The circumference is ≈ 31.416 units.
Frequently asked questions
How many diameters fit around a circle?
About 3.14159 — that is exactly π. It is why circumference problems always involve π.
Can I get circumference from area?
Yes: find the radius first with r = √(A ÷ π), then double it and multiply by π. Selecting Area in this calculator does both steps for you.
Circumference vs perimeter — same thing?
Circumference is the perimeter of a circle specifically. Polygons use “perimeter”; circles use “circumference.”
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