Circumference to Radius Calculator
Convert a circle's circumference directly to its radius with r = C ÷ (2π). Diameter and area are calculated automatically from the same input.
r = C ÷ (2π)
- 1
Circumference (input)
44 - 2
Radius
44 ÷ (2 × π) = 7.002817Rearranging C = 2πr gives r = C ÷ (2π).
How does this calculator work?
Radius equals circumference divided by 2π: r = C/(2π). For C = 44: r ≈ 7.003. From radius, diameter d = 2r and area A = πr². Most useful when you can wrap a tape around a circular object to measure its perimeter but cannot measure straight across it.
Formula
How this is calculated
The circumference formula is C = 2πr. Dividing both sides by 2π isolates the radius: r = C/(2π). This is an exact algebraic rearrangement — no approximation is introduced beyond the precision of π itself.
From the radius, the diameter is d = 2r = C/π, and the area is A = πr² = C²/(4π). All three quantities follow from a single circumference measurement, which makes this useful whenever you can measure the perimeter of a circular object directly but not its cross-sectional width.
Common practical uses include finding the radius of a tree trunk, a cylindrical tank, a wheel rim, or a circular sports field when only the outer perimeter is accessible. Wrap a measuring tape around the object to get C, then enter it here. The result is in the same length unit as the circumference you enter.
Frequently asked questions
r = C ÷ (2π). For a circumference of 44: r = 44 / (2 × 3.14159) ≈ 7.003.
Wrap the tape measure around the object to get the circumference C, then compute r = C/(2π). Enter C above and the calculator gives the radius immediately.
r = 100 / (2π) ≈ 15.916. The diameter is double that: d ≈ 31.831, and the enclosed area is πr² ≈ 795.77 square units.
TG we-Calculate Editorial Team. (2026). Circumference to Radius Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/circumference-to-radius-calculator
TG we-Calculate Editorial Team. "Circumference to Radius Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/circumference-to-radius-calculator.
TG we-Calculate Editorial Team, "Circumference to Radius Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/circumference-to-radius-calculator
@misc{wecalculate_circumference_to_radius_calculator, title = {Circumference to Radius Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/circumference-to-radius-calculator}}, year = {2026}, note = {TG we-Calculate} }
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