⭕ Circle Calculator

Find any circle measurement — area, circumference, diameter, or radius — from any one known value.

⭕

Circle Calculator

Math

Inputs

Known Value*

Value*

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How to Use This Calculator

1
Select which measurement you already know.
2
Enter its value.
3
Click Calculate to see all other circle measurements.

How It Works

All circle measurements derive from radius r: Diameter = 2r, Circumference = 2πr, Area = πr². Enter any one known value and the calculator computes all others.

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Dedicated URL:circle-calculator.ultimatetools.online

Frequently Asked Questions

Radius is from center to edge. Diameter = 2 × radius, passing through the center from edge to edge.

Why Use This Tool

Instant, accurate results
No registration required
100% free forever
Works on all devices
Privacy — no data stored