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Enter any one of a circle's radius, diameter, circumference or area to get all the others instantly.
Also covers: Circumference calculator Β· Radius from area Β· Diameter calculator
Radius (r)
5 cm
Diameter (d = 2r)
10 cm
Circumference (C = 2Οr)
31.415927 cm
Area (A = ΟrΒ²)
78.539816 cmΒ²
Working
Radius, diameter, circumference, or area.
All four values appear, with the formula used.
d = 2r, C = 2Οr = Οd, and A = ΟrΒ².
Divide by 2Ο: a circumference of 31.4 cm gives r β 5 cm.
Calculations use Ο to about 16 significant digits, far more than any practical measurement needs.
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