1. What is Radius?

The radius of a circle is the distance from the center of the circle to any point on its circumference. It is half the length of the diameter and is a fundamental measurement in circular geometry.

2. How to Calculate Radius from Diameter

The formula to calculate radius from diameter is simple:

Where:

• Radius — Distance from center to edge of circle
• Diameter — Straight line passing through center, connecting two points on circumference

Explanation: Since diameter is the longest distance across a circle (passing through the center), the radius is exactly half of this distance.

3. Practical Applications

Details: Knowing the radius is essential for calculating circumference (\(2\pi r\)), area (\(\pi r^2\)), and for many engineering and construction applications involving circular shapes.

4. Using the Calculator

Tips: Simply enter the diameter measurement in any units, and the calculator will provide the radius in the same units. The diameter must be a positive number.

5. Frequently Asked Questions (FAQ)

Q1: Can I calculate diameter from radius?
A: Yes, diameter = 2 × radius. Just multiply the radius by 2 to get the diameter.

Q2: Are radius and diameter always in the same units?
A: Yes, both measurements are linear and use the same units (cm, inches, meters, etc.).

Q3: Does this work for spheres as well as circles?
A: Yes, the relationship between radius and diameter is the same for both circles (2D) and spheres (3D).

Q4: What if I have circumference instead of diameter?
A: You can calculate radius from circumference using: radius = circumference / (2π).

Q5: Why is radius important in geometry?
A: Radius is a fundamental measurement that appears in most formulas related to circles and spheres, making it essential for calculations.