Tech-Info 06: A distinction is made between the nominal rope diameter and the actual rope diameter.

The nominal wire rope diameter is an agreed theoretical value for the diameter of the smallest circle enclosing the outer strands.The effective rope diameter, also called actual rope diameter, is the diameter of the smallest circle enclosing all outer strands, as measured on the rope itself. The tolerance range for the effective rope diameter is specified in related national and international standards. According to EN 12385-4 it is between -0% and +5% (for nominal rope diameters ≥ 8mm)This means that the effective rope diameter upon delivery must neither be smaller, nor 5% bigger than the nominal rope diameter.The tolerance range is often higher for smaller ropes like 3mm to 7mm nominal diameter.In the Oil and Gas industry, which is firmly based on US regulations, a tolerance range from -1% to +4% is applied.The effective rope diameter changes depending on the load applied. Therefore the effective rope diameter should in critical cases be measured on a rope that is loaded with 5% of the calculated breaking strength.