Method #1 – Diameter from Area
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Formula – How to calculate the diameter of a circle from the area
π is approximately 3.1415926535
Diameter = 2 x (√(Area ÷ π))
Example
A circle has an area of 10
Diameter = 2 x (√(10 ÷ π) = 2 x (√(10 ÷ 3.14159) = 2 x √(3.1831) = 2 x 1.7841 = 3.5682
Method #2 – Diameter from Circumference
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Formula – How to calculate the diameter of a circle from the circumference
π is approximately 3.1415926535
Diameter = Circumference ÷ π
Example
A circle has a circumference of 10
Diameter = 10 ÷ π = 10 ÷ 3.14159 = 3.1831
Method #3 – Diameter from Radius
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Formula – How to calculate the diameter of a circle using the radius
π is approximately 3.1415926535
Diameter = Radius x 2
Example
A circle has a radius of 10
Diameter = 10 x 2 = 20