Pi meters. (About 3.14 meters)
Found by multiplying 1 meter by pi.
Assuming by length you mean the distance around the circle.
A diameter is a description of a line from one side of a circle to the opposite side. Its length depends on the size of the circle.
Diameter of the circle: 2 times 1 = 2 meters
The radius is 1/2 of the diameter. A diameter of 10 has a radius of 5.
A circle with a diameter of one meter has an area of 0.785 square meters.
50 centimeters
If the diameter is 1 metre then the radius is 0.5 metre.
The volume of a pipe with diameter of 1 meter and a length of 2 meters is 1.57 cubic meters.
Length of diameter:length of radius = 2:1
A circle with a diameter of 1 metre has an area of pi/4 square metres.
pi ( = 3.1416 approx) metres.
Circumference of a circle = 2*pi*radius or diameter*pi
By definition the radius of a circle is a straight line drawn from the centre of a circle to its circumference. If you extend that line to the opposite side of the circle it becomes the diameter. The length of the diameter is twice the length of the radius. If the radius is 1316 the diameter is 2632