Circle Calculator: Radius, Diameter, Circumference, and Area
A circle calculator computes all key properties of a circle from any single known measurement. Whether you have the radius, diameter, circumference, or area, this tool instantly derives every other property using fundamental circle formulas.
Circle Formulas
All circle calculations are based on the mathematical constant pi. The key relationships are:
Diameter = 2r | Circumference = 2πr | Area = πr²
Where r is the radius and pi is approximately 3.14159265.
Working Backwards
Given the circumference, the radius is C / (2 pi). Given the area, the radius is the square root of (A / pi). From the radius, all other values follow directly.
Practical Applications
- Engineering: Calculating pipe cross-sections and material requirements.
- Construction: Determining the amount of fencing needed for circular plots.
- Design: Sizing circular elements in graphic and web design.
- Science: Computing orbital paths, lens areas, and circular motion parameters.
Frequently Asked Questions
How precise is the value of pi used?
This tool uses JavaScript's Math.PI constant, which provides pi to approximately 15 significant digits (3.141592653589793). Results are displayed rounded to 6 decimal places.
Can I calculate arc length or sector area?
This tool focuses on full-circle properties. For arc and sector calculations involving a specific angle, you would need a dedicated arc calculator tool.