Crane Lift Load Chart / SWL Calculator

SWL = Safe Working Load (also called WLL, Working Load Limit). Calculates rigging sling tension per leg using standard ASME B30.9 load-angle geometry, and compares your total lift weight against your crane's own rated capacity at the working radius.

Critical scope limitation — please read: Real crane capacity charts (the load-vs-radius curves for a specific make/model, boom length, and configuration) are proprietary, manufacturer-specific documents — there is no universal formula that can replicate them, and this calculator does not attempt to. This tool only does two things: (1) calculates sling/rigging tension from standard, non-proprietary rigging geometry, and (2) compares your total lift weight against a crane rated capacity figure that you must look up yourself from your specific crane's current, certified load chart for the actual radius, boom length, and configuration in use. Never substitute a generic number for your crane's real chart. A qualified rigger and a qualified crane operator must review every lift.

Load & Rigging

Load Weight (lbs)

Rigging / Hook Block / Below-the-Hook Weight (lbs)

Sling Configuration

Legs Sharing the Load Evenly For 3–4 leg bridles, ASME/OSHA guidance conservatively credits only 2 legs as load-sharing unless a qualified rigger has verified equalization.

Hitch Type

Sling Angle from Horizontal (°) Measure from horizontal, not vertical. Below 30° is not recommended without a qualified-person critical lift plan.

Sling Tag Vertical WLL, per leg (lbs) From the actual sling tag/manufacturer chart — vertical hitch rating.

Crane Capacity Check (Optional)

Crane Rated Capacity at This Radius/Configuration (lbs) Look this up from your specific crane's current certified load chart. Leave blank to skip this check.

0 lbs

Total Lift Weight

0 lbs

Tension per Leg

Sling Utilization

Formula Reference

Total Lift Weight = Load Weight + Rigging/Hook Block Weight
Load Angle Factor (LAF) = 1 ÷ sin(Sling Angle from Horizontal)
Tension per Leg = (Total Lift Weight ÷ Legs Sharing Load) × LAF
Effective Sling WLL = Tag Vertical WLL × Hitch Factor
Sling Utilization % = Tension per Leg ÷ Effective Sling WLL × 100

Reference Values

Wire rope sling design factor	5:1 (per ASME B30.9 — already built into the tag WLL)
Recommended minimum sling angle	30° from horizontal (below this, a qualified-person critical lift plan is required)
Choker hitch factor	~75–80% of vertical tag WLL
Basket hitch factor	up to 200% of vertical tag WLL (both legs vertical, D/d ratio respected)