Chain Sling WLL Calculator

Grade 80 (alloy chain per EN 818-2) is the standard for overhead lifting. Grade 100 is higher-tensile alloy chain with approximately 25% greater WLL for the same chain size. Both require colour-coded tags and regular inspection. Grade 100 is preferred where weight savings matter, but both grades are fully acceptable for lifting.

Total capacity = (number of legs) × (single-leg WLL) × sin(angle). At 90° (vertical), sin = 1, so total = n × WLL. At 60°, capacity is 86.6% of vertical. At 45°, it is 70.7%. At 30°, only 50%. The single-leg WLL at any angle is always the maximum tension the chain can handle.

ASME B30.9 recommends sling angles no less than 30° from horizontal. Below 30°, leg tension exceeds twice the vertical share per leg, and horizontal compression forces on the load become extreme. Use a spreader beam to keep angles above 45°.

Grade is stamped on each link in the master link, coupling links, and chain body. Grade 80 chains are typically painted red or brown; Grade 100 are painted blue or orange. Always verify grade markings — never use an unmarked chain for lifting.

ASME B30.9 requires inspection before each use. Annual documented inspection by a qualified person is the minimum; quarterly inspection in severe service. Remove from service if: any link is worn more than 10% of original diameter, elongated more than 3% of rated length, bent, twisted, heat-damaged, or has gouges or surface cracks.

Grade 80 chain slings may be used up to 200°C with no derating. From 200°C to 300°C, reduce WLL by 10%. From 300°C to 400°C, reduce by 25%. Do not use above 400°C. Always check manufacturer data and inspect after each high-temperature use. Grade 100 chains have similar temperature limits — check the product datasheet.

The master link (or oblong master link) is the large oval link at the top of the sling that attaches to the crane hook. Coupling links connect the chain legs to the master link. Both are component parts of the sling assembly and must be rated to match the chain WLL.

A perfectly vertical 2-leg sling does give 2× single-leg WLL. But at any angle below 90°, each leg must support its vertical share plus a horizontal tension component. The angle factor sin(θ) reduces the useful vertical contribution of each leg. At 45°, a 2-leg sling has only 1.414× (not 2×) the vertical capacity of one leg.