Circle Calculator

Free online circle calculator tool.

Radius

What Is a Circle Calculator?

The Circle Calculator is a dual-purpose tool that computes both the area and the circumference of a circle simultaneously based purely on its radius. This free online tool is useful for circle calculator, circle area calculator, circumference calculator. Common use cases include geometry, radius calculations, circular objects, construction, and area or circumference calculations. It is designed for quick browser-based calculations and is suitable for homework, programming, study, everyday math, and checking results.

How to Use This Circle Calculator

1
Enter RadiusType the distance from the center of the circle to its edge.
2
CalculateThe tool evaluates πr² and 2πr.
3
Review AreaThe circle's area is returned in square units.
4
Review CircumferenceThe boundary length is returned in linear units.
5
Check UnitsKeep the radius in the unit you want reflected in the result.

Frequently Asked Questions

The diameter is exactly twice the radius. Simply divide your diameter by 2, and enter that number into the radius field.

This calculator uses the standard IEEE 754 floating-point Pi provided by JavaScript engines, which is accurate to 15 decimal places.

Circumference is the specific mathematical term for the perimeter of a circle—it represents the total length of the circular boundary.

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