# How to measure wire rope diameter

The actual diameter of a wire rope is the diameter of a circumscribed circle that will enclose all the strands. It ‘s the largest cross-sectional measurement as shown here. You should make the measurement carefully with calipers.

The illustrations show the correct and incorrect methods of measuring wire ropes with even numbers of outer strands.

As we move toward metric measurements, it will become increasingly necessary to convert English units into Sl – International System of Units – (or metrics), and vice versa.

### Metric conversion and equivalents

#### ROPE DIAMETER

For standard, general purpose wire ropes, in measuring diameter, the industry is leaning toward a “soft” conversion to metric during the transition period. For example, a 1″ diameter rope converts to 25.4 mm in metrics. Using the soft conversion, this is changed to the whole metric size that most nearly parallels the 1″ size range, or 26 mm. In sizes smaller than 5/8′: the rope diameter is rounded to the nearest 0.5 mm.

#### STRENGTHS AND WEIGHTS

The following table gives the closest equivalent metric diameters for rope sizes up through 5 inches. Again , these metric sizes are based on the industry’s “soft” conversion. Your application may have tighter tolerances that require a hard conversion. Therefore, the values in the table would not apply.

Inches Millimeters Inches Millimeters Nominal wire rope diameter 1/4 6.5 2 1/8 54 5/16 8 2 1/4 58 2 9.5 2 3/8 60 7/16 11.5 2 1/2 64 1/ 2 13 2 5/8 67 9/16 14.5 2 3/4 71 5/8 16 2 7/8 74 3/4 19 3 77 7/8 22 3 1/8 80 1 26 3 1/4 83 1 1/8 29 3 3/8 87 1 1/4 32 3 1/2 90 1 3/8 35 3 3/4 96 1 1/2 38 4 103 1 5/8 42 4 1/4 109 1 3/4 45 4 1/2 115 1 7/8 48 4 3/4 122 2 52 5 128

Since rope minimum breaking force and weight per unit of length vary for different types and grade of ropes, the following conversion factors are given to help you convert the figures you need:

• To convert rope weight in pounds per foot (lb/ft) to kilograms per meter (kg/m), multiply by 1.488.
• To convert rope minimum breaking force in tons (T) to kilonewtons (kN), multiply by 8.897; 1 lb equals 4.448 newtons (N).
• To convert rope minimum breaking force in tons (T) to kilograms (kg), multiply by 907.2.

`Note: The newton (a unit of force) is the correct unit for measurement of minimum breaking force in the Sl system of units. We have included a conversion f`