Radius Calculator - Find Radius from Diameter Formula
IP331.com | Online Tools
Algebra ToolsGeometry ToolsTrigonometry ToolsMatrix ToolsFunction ToolsNumber Theory ToolsBase ConverterElectronics & PhysicsStatistics ToolsLife & Finance
Home›Geometry Tools›Radius Calculator

Radius Calculator

Find circle radius from diameter

Radius Formula

r = d / 2

The radius is the distance from the center of a circle to its edge. Because the diameter spans the circle through the center, the radius is exactly one half of the diameter.

⚠This calculator uses diameter as the input. Diameter must be zero or positive.

How Radius Works

Radius controls the size of a circle and appears in almost every circle formula, including area, circumference, arcs, and sectors.

Center to Edge

Radius starts at the center.

Half Diameter

r equals d divided by 2.

Circle Size

Larger radius means larger circle.

Formula Base

Area and circumference both use radius.

💡 Example: If d=14, r=14/2=7.

Applications of Radius

Circle AreaCircumferenceArc LengthEngineering Design

Frequently Asked Questions

What is a radius calculator?▼
It calculates circle radius from diameter.
What is the radius formula?▼
From diameter, the formula is r=d/2.
How do I use this calculator?▼
Enter the diameter and click Calculate to get the radius.
Can radius be negative?▼
No. Radius is a distance and cannot be negative.
Where is radius used?▼
Radius is used in circle area, circumference, arcs, sectors, and circular design.

More Geometry Tools

Algebra Tools Geometry Tools Trigonometry Tools Matrix Tools Function Tools Number Theory Tools Base Converter Electronics & Physics Statistics Tools Life & Finance

Free online calculators and tools covering mathematics, unit conversion, text processing, and daily life. Accurate, fast, mobile-friendly, and completely free to use.

© 2026 IP331.com — Free Online Tools. All rights reserved.

About · Contact · Privacy Policy · Cookie Policy · Terms of Use · Disclaimer · Sitemap