How do you find the circumference of a semi-circle?

The length (circumference) of the curved part of a semi-circle is pi times the radius (pi*R). If the diameter is given, then the semi-circle length is 1/2 (pi * x D) because the radius is 1/2 of the diameter.

(There are 2pi radians in a full circle.)

A closed shape formed from a semi-circle has a perimeter P = D + (pi * D / 2)

(diameter plus the curved part)