Geometry
Enter any one measurement and the rest solve themselves — radius, diameter, circumference, or area.
About this tool
Every circle measurement is derived from the same constant, π. Give this tool any single value — radius, diameter, circumference, or area — and it works backward and forward through the formulas to fill in the rest.
Constant used
π ≈ 3.14159
All results use full double-precision π, then round for display.