Radius to Diameter
Convert any radius value to its diameter instantly. The diameter is exactly twice the radius. Enter the radius below to get the result.
Radius to Diameter Formula
To find the diameter from a known radius, simply multiply the radius by 2:
d = 2r
The diameter d equals 2 times the radius r. This is the simplest circle conversion — the diameter is always exactly twice the radius.
For example, find the diameter of a circle with a radius of 5:
d = 2 × 5 = 10
The diameter of this circle is 10.
Frequently Asked Questions
Multiply the radius by 2. The formula is d = 2r. For example, a radius of 5 gives a diameter of 10. This works in any unit.
d = 2 × 7.5 = 15. The diameter is 15 units.
The radius measures from the center to the edge. The diameter measures from edge to edge through the center — so it spans two radii. By definition, d = 2r.