← All Free Tools

Rigging Sling Angle & Load Calculator

Sling tension per leg from load, leg count and angle — including the ASME B30.9 conservative multi-leg rule.

Sling geometry

Sling angle from horizontal (°)

Load weight (kg)

Number of sling legs

Sling WLL at vertical (optional) (kg)

Tension per leg (conservative)

–

Sling angle from horizontal

–

Load factor (1 ÷ sin θ)

–

Why "conservative" tension uses only 2 legs: per ASME B30.9 practice, a 3- or 4-leg bridle sling's rated capacity is based on only two legs carrying the full load — you can't guarantee all legs share load equally, since that depends on the load's exact centre of gravity, hook/pick-point tolerances, and rigging fabrication. This tool follows that rule for 3/4-leg slings; the "idealized equal-share" figure is shown alongside for reference only and should not be used for capacity decisions.

How this is calculated

Tension per leg = (Load ÷ effective legs) ÷ sin(sling angle from horizontal). For a 2-leg sling, effective legs = 2. For 3- or 4-leg bridles, effective legs = 2 as well, per ASME B30.9's conservative practice of assuming only the two most heavily loaded legs carry the full weight. The load factor (1 ÷ sin θ) shows how sharply tension rises as the sling angle flattens: at 90° (vertical) the factor is 1.0, at 45° it's 1.41, at 30° it's 2.0, and below 30° it climbs steeply — which is why most rigging standards treat 30° from horizontal as a practical minimum and call for engineered rigging below that. When headroom and spread are given instead of an angle, angle = atan(headroom ÷ horizontal distance) and required sling length = √(headroom² + horizontal distance²).