1. What is the Circle Radius Formula?

The circle radius formula calculates the radius of a circle when you know its circumference. The radius is the distance from the center of the circle to any point on its edge.

2. How Does the Calculator Work?

The calculator uses the circle radius formula:

Where:

• \( r \) — Radius of the circle (length units)
• \( C \) — Circumference of the circle (length units)
• \( \pi \) — Mathematical constant Pi (~3.14159)

Explanation: The formula divides the circumference by 2π to find the radius, since the circumference is equal to 2πr.

3. Importance of Radius Calculation

Details: Knowing the radius of a circle is fundamental in geometry, engineering, and many practical applications like construction, manufacturing, and design.

4. Using the Calculator

Tips: Enter the circumference in any length unit (meters, feet, inches, etc.). The result will be in the same units. Value must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What if I know the diameter instead of circumference?
A: The radius is simply half of the diameter (r = d/2). No need to use this calculator.

Q2: What units should I use?
A: Any length units can be used (meters, feet, inches, etc.), just be consistent.

Q3: How precise is the value of π used?
A: The calculator uses PHP's built-in pi() function which provides sufficient precision for most practical applications.

Q4: Can I calculate circumference from radius?
A: Yes, using the inverse formula: C = 2πr.

Q5: What's the relationship between radius and area?
A: Area is calculated as A = πr², which is different from the circumference formula.