Circumference of a circle
Use circumference = pi * diameter (pi approx. 3.14) to find a circle's circumference from its radius or diameter, or its diameter from its circumference. Unlimited questions, five difficulty levels, and a full worked solution every time — free.
Try one
A manhole cover has a diameter of 13 cm. Using pi = 3.14, what is its circumference?
Answer: 40.82
See one solved, step by step
A circular rug has a radius of 3 cm. Using pi = 3.14, what is its circumference?
📘 Worked solution
1diameter = 2 · radius = 2 · 3 = 6The diameter is always twice the radius.
2C = π · d = 3.14 · 6Circumference is pi times the diameter; we'll use 3.14 for pi.
3= 18.84 cmMultiply it out.
Ready to master it?
Jump into unlimited practice — your Winny Score tracks you to 100. And if it won't click, a real tutor will make it click: first lesson free.
Start practicing