How it works
When a sling leg is not vertical, it carries more than its share of the weight because part of its tension pulls sideways. The lower the angle from horizontal, the larger the multiplier.
Divide the weight among the legs, then multiply by 1 ÷ sin(angle). At 90° (vertical) the factor is 1. At 60° it is 1.155, at 45° it is 1.414, and at 30° it is 2.
Worked example
A 2,000 lb load lifted with a two-leg sling at 60° from horizontal:
- Angle factor = 1 ÷ sin(60°) = 1.155
- Tension per leg = (2,000 lb ÷ 2 legs) × 1.155 = 1,154.7 lb
| Input | Value |
|---|---|
| Load weight | 2000 lbf |
| Number of legs carrying the load | 2 |
| Sling angle from horizontal | 60 ° |
| Result | Value |
|---|---|
| Tension per leg | 1,154.7 lbf |
| Angle load factor | 1.155 × |
Assumptions and limits
- Assumes a symmetrical lift with the center of gravity between the lifting points and equal leg angles.
- Does not include dynamic or shock loading, sling wear, hitch (choker) reductions, or hardware limits. Add a margin for these.
- Your sling's working load limit must exceed the computed tension for its actual hitch and angle.
Common questions
What is the minimum safe sling angle?
Most rigging references recommend not going below 45° from horizontal and treat 30° as an absolute minimum, because leg tension doubles at 30°.
Is the angle measured from horizontal or vertical?
This calculator uses the angle from horizontal. If you measured from vertical, subtract it from 90°.
Do I include the sling weight?
Include the weight of rigging hardware, spreader bars, and hooks in the load weight.
Sources
- Statics: leg tension = load share ÷ sin(angle from horizontal).
- For sling ratings and use limits see ASME B30.9 and OSHA 29 CFR 1910.184.
Updated 2026-09-30