Diameter Calculator
Calculate the diameter of a circle from radius, circumference, or area. The diameter is the longest chord passing through the center.
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Frequently Asked Questions
What is the diameter of a circle?
The diameter is the longest straight line that can be drawn through a circle, passing through the center. It's exactly twice the radius.
How do you find diameter from radius?
Multiply the radius by 2: d = 2r. For example, if the radius is 5, the diameter is 10.
How do you find diameter from circumference?
Divide the circumference by π: d = C/π. This comes from rearranging the formula C = πd.
How do you find diameter from area?
Use d = 2√(A/π). First find the radius using r = √(A/π), then multiply by 2 to get the diameter.
Is diameter always the longest chord?
Yes, the diameter is always the longest chord in a circle. Any chord that doesn't pass through the center will be shorter than the diameter.
What's the difference between diameter and radius?
The radius extends from the center to the edge, while the diameter extends from one edge through the center to the opposite edge. The diameter is always twice the radius.
Can a circle have multiple diameters?
A circle has infinite diameters (any line through the center), but they all have the same length.
Why is diameter important?
Diameter is commonly used in engineering and manufacturing specifications, pipe sizing, wheel measurements, and many practical applications where circle dimensions are needed.