Circumference Calculator
Find the circumference, area, diameter, and radius of a circle from any single known dimension.
Circumference Calculator
Calculate circumference, area, diameter, and radius of a circle
Radius
5
Diameter
10
Circumference
31.416
Area
78.54
Understanding Circle Geometry Metrics
The circumference is the total linear distance around the outer boundary of a circle, analogous to the perimeter of a polygon.
Core Circle Formulas
Circumference
C = 2 π r
Circle Area
A = π r²
Diameter
d = 2r
Manual Calculation Walkthrough
Calculate the circumference and area of a circular garden with a radius of 7 meters:
- Circumference: C = 2 × 3.14159 × 7 = 43.98 meters.
- Area: A = 3.14159 × 7² = 3.14159 × 49 = 153.94 square meters.
Frequently Asked Questions
What is the origin of Pi (π)?
Pi is defined as the ratio of a circle's circumference to its diameter (C / d = π). Regardless of the size of the circle, this ratio remains constant.
How do you measure circumference physically?
Wrap a flexible measuring tape around the outer edge of the object, or wrap a piece of string around the object, mark the overlap, and measure the string against a straight ruler.
Save Configuration Snapshot
Save current parameters to your dashboard for instant one-click reloading.
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ConstructionAbout This Calculator & Guide
About the Circumference— Radius, Diameter & Circle Area Calculator
The circumference of a circle is the linear distance around its outer boundary. In geometry, the ratio of any circle's circumference to its diameter is always constant and represented by the mathematical constant Pi (π ≈ 3.14159). This calculator allows you to solve for radius, diameter, area, or circumference from any single known input.
Formula & Calculation Method
The standard mathematical relationship used for this calculation is:
Worked Step-by-Step Example
For a circle with a radius of 5 cm: Circumference C = 2 * π * 5 ≈ 31.42 cm. Area A = π * 5² ≈ 78.54 cm².
How to Use
- Choose your input parameter (Radius, Diameter, Circumference, or Area).
- Input the numerical value in the field.
- The calculator computes the other three circle dimensions automatically in real-time.
FAQ
Frequently Asked Questions
What is the formula for the circumference of a circle?+
The circumference of a circle is calculated using C = 2 × π × r (where r is radius) or C = π × d (where d is diameter).
How do you calculate circle area from circumference?+
To find area (A) directly from circumference (C), use the formula A = C² / (4π).
What is the relationship between radius and diameter?+
The diameter (d) is twice the length of the radius (r): d = 2r.
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