Determining the exact length of a V belt with a mathematical equation becomes confusing. This holds especially true when measuring the length of a V belt running between two pulleys with different diameters and do not have experience using calibres to measure the diameter of the drive pulleys. Fortunately, you have an alternative to determine the length of a V belt accurately that does not require the use of a complicated mathematical formula or complicated measuring equipment.

Place a mark on the side of an old V belt with a white paint marker.

Set the flat outer edge of the V belt on a flat surface. Rotate the V belt to place the paint mark against the flat surface. Draw a mark on the flat surface with a pencil to designate the starting point of the measurement.

Roll the V belt along the flat surface until the paint mark rolls back to the flat surface. Place a second pencil mark on the flat surface to designate the contact point of the paint mark with the flat surface.

Measure the distance between the two pencil marks to determine the circumference of the V belt.

Wrap 1/4 inch nylon rope around both pulleys. Overlap 4 inches of the nylon rope.

Draw a line across the nylon rope with a black permanent marker. Make sure the mark crosses both sections of overlapped nylon rope.

Lay the marked nylon rope on a flat surface.

Measure the distance between the two marks with a tape measure to determine the circumference of the needed V belt.