How it Works
1. Enter one known value (e.g., Radius). 2. The tool applies πr² for Area and 2πr for Circumference. 3. View all results.
What is Circle Calculator (Radius, Diameter, Area, Circumference)?
A geometry tool that solves for Radius, Diameter, Circumference, and Area instantaneously.
Example
Input: Radius 5
Result: Area: 78.54
FAQ
What is Pi?
Pi (π) is the ratio of a circle's circumference to its diameter, approx 3.14159.
How to find area from diameter?
Divide diameter by 2 to get radius, then use πr².
Is circumference the perimeter?
Yes, circumference is the linear distance around the circle.
Relationship between Radius and Diameter?
Diameter is exactly 2x the Radius.
Real world use?
Calculating material for round tables, fencing for circular pools, or wheel distance.