Circumference Calculator
Free online Circumference Calculator.
Calculator
How to Use
- Enter the required values
- Click Calculate to see the result
- Review the detailed output
Formula
C = 2 x pi x r = pi x d, where r = radius, d = diameter, pi = 3.14159. From area: r = sqrt(A/pi), then C = 2 x pi x r.
Example Calculations
From Radius
Input: Radius: 7 cm
Result: Circumference: 43.98 cm
From Diameter
Input: Diameter: 10 inches
Result: Circumference: 31.42 inches
From Area
Input: Area: 50 sq m
Result: Radius: 3.99 m, Circumference: 25.07 m
About This Calculator
Free online circumference calculator. Calculate instantly in your browser with our easy-to-use tool. No sign-up required.
Our circumference calculator is free, easy to use, and provides instant results. All calculations are performed in your browser for privacy and speed.
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Frequently Asked Questions
Calculate circumference?
C = 2 x pi x r, or C = pi x d. Radius 5: C = ~31.42.
What is pi?
Ratio of circle circumference to diameter (~3.14159). Appears in circle, sphere, and periodic formulas.
Circumference from area?
r = sqrt(Area/pi), then C = 2 x pi x r.
Circumference of ellipse?
No simple exact formula. Ramanujan approximation: C ~ pi x [3(a+b) - sqrt((3a+b)(a+3b))].
Real-life uses?
Engineering (pipes, wheels), sports (tracks), astronomy (orbits), everyday measurements.