Method #1 – Circumference from Radius
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Formula – How to calculate the circumference of a circle using the radius
π is approximately 3.1415926535
Circumference = 2 x π x Radius
Example
A circle has a radius of 10
Circumference = 2 x π x 10 = 2 x 3.14159 x 10 = 62.83
Method #2 – Circumference from Diameter
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Formula – How to calculate the circumference of a circle from the diameter
π is approximately 3.1415926535
Circumference = π x Diameter
Example
A circle has a diameter of 10
Circumference = π x 10 = 3.14159 x 10 = 31.4159
Method #3 – Circumference from Area
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Formula – How to calculate the circumference of a circle using the area
π is approximately 3.1415926535
Circumference = 2 x √(π x Area)
Example
A circle has an area of 10
Circumference = 2 x √(π x 10) = 2 x √(3.14159 x 10) = 2 x √(31.4159) = 2 x 5.605 = 11.21