Circle Calculator

Calculate the radius, diameter, circumference, and area of a circle.

Circle Calculator

Enter any value to calculate the others.

Radius (r)

Diameter (d)

Circumference (C)

Area (A)

Enter values to visualize

Understanding the Circle Calculator

Instantly determine the radius, diameter, circumference, and area of any circle by entering just one known dimension.

Guide

How to use the Circle Calculator

1Enter any single known value: Radius, Diameter, Circumference, or Area.
2The calculator immediately solves for all other interconnected metrics.
3Use the interactive visual diagram to see your circle scaled according to your input.
4Check the results, which are rounded to 4 decimal places for maximum precision.

Applications

Common Use Cases

Construction: Sizing circular footings or architectural columns.

Landscaping: Planning circular garden beds or patio layouts.

Engineering: Designing mechanical parts with specific circular tolerances.

Education: Verifying geometry and trigonometry homework.

The Maths Behind the Calculation

C = 2πr, A = πr²

The relationship between a circle's core components is constant, defined by the mathematical constant Pi (π), which is approximately 3.14159.

Knowledge Base

Frequently Asked Questions

How do I calculate radius if I only have the area?

You can find the radius by dividing the area by Pi (π) and then taking the square root of the result: r = √(A / π).

How accurate is the calculation?

Our tool uses the standard JavaScript Math.PI constant (approx. 3.141592653589793) for calculations, providing results far more accurate than manual estimates.

Can I use different units of measure?

Yes. The calculator is unit-agnostic; if you enter dimensions in inches, all resulting values will correspond to inches (or square inches for area).

Regional Notice: United States

"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."

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