How to use the wire rope safe working load calculator
Divide the minimum breaking load on the certificate by the safety factor and you have the load one leg of rope may carry. Add the number of legs and the angle from vertical and the allowable vertical load of the whole set appears with the angle factor already applied.
The relations applied are safe working load = minimum breaking load divided by the safety factor, and an angle factor equal to the cosine of the angle between the rope and the vertical. The allowable vertical load of the set is the per-leg load times the number of legs times that factor. Enter the breaking load in tons of 2,000 lb or in pounds, as US rope catalogs list it, and the angle in degrees; results are shown in pounds with tons and kilonewtons in parentheses. For example, a breaking strength of 13.3 tons (26,600 lb) at a safety factor of 5 gives 5,320 lb (23.66 kN) per leg, and two legs at 30 degrees from vertical give about 9,215 lb. As the angle approaches 90 degrees the vertical component tends to zero, so 90 and above is not calculated and a notice appears instead. Beyond 60 degrees from vertical (30 degrees to horizontal) tension climbs steeply, so a warning is shown in line with the limit many rigging guides set. Values are as of October 2026, so read them with the rope certificate and the standard you apply.
Rope self weight, breaking load estimated from core type, and corrections for the hitch method are not covered. Required safety factors and breaking loads by rope grade were not confirmed in an authoritative source, so no values are suggested and you enter your own. The calculation assumes tension shared evenly between the legs, so eccentric loads, shock loads and wear are not reflected. This calculator is for reference and does not replace design. Review by a qualified engineer is required.
Frequently asked questions
Estimating breaking load from rope diameter and core type is not covered. Enter the minimum breaking load from the maker certificate or catalog for the result to mean anything.
Required or recommended safety factors were not confirmed in an authoritative source, so no value is suggested. Enter the figure from the standard or the in-house rule you work to.
From the vertical. A straight vertical lift is 0 degrees, and as the angle grows the angle factor falls and the allowable vertical load drops with it.