Geometry
Circumference from the diameter
The same formula with the doubling already done, since the diameter is twice the radius.
The Formula
C = pi x d
The same formula with the doubling already done, since the diameter is twice the radius.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| C | Circumference | metres | Distance around the circle. |
| d | Diameter | metres | Distance straight across the widest part. |
What Each Symbol Means
Cmetres
Circumference
Distance around the circle.
dmetres
Diameter
Distance straight across the widest part.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate the circumference of a circle page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate The Circumference Of A Circle, filed under Math. Every number the guide produces comes from substituting into this one line.