CircleLab

Circle Circumference

The distance around a circle, from its radius.

Circumference vs. area

Circumference grows linearly with radius (double r, double C) while area grows with the square of r — a useful distinction when you're buying trim (linear, circumference) versus flooring (area).

Real uses

Fencing a circular pool, sizing a belt or chain that wraps a wheel, or figuring out how far a wheel of known diameter travels in one rotation all come down to this formula.

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CircleLab

Circle Circumference

The distance around a circle, from its radius.

Radius

Circumference

31.416

C = 2π · r

Area: 78.54

What you entered

Radius: 5

1
Diameter
2 × 5= 10
2
Circumference
2π × 5= 31.4159
3
Area
π × 5²= 78.5398

Result

Circumference: 31.416

A circle with radius 5 has a circumference of 31.416 units.

Circumference vs. area

Circumference grows linearly with radius (double r, double C) while area grows with the square of r — a useful distinction when you're buying trim (linear, circumference) versus flooring (area).

Real uses

Fencing a circular pool, sizing a belt or chain that wraps a wheel, or figuring out how far a wheel of known diameter travels in one rotation all come down to this formula.