How to use this calculator
- Enter the total suspended load. Include the lifted item and any below-the-hook rigging carried by the sling set.
- Set the loaded legs. Count only the sling legs that actually share the load.
- Choose the angle input. Use angle from horizontal when you have it, or included angle for a symmetric bridle.
- Enter per-leg WLL. Use the rated capacity that applies to the sling type and hitch before this angle screen.
- Review tension and utilization. Compare leg tension, angle factor, total capacity at angle and WLL utilization before moving to a lift plan.
How it works
The vertical component of all loaded sling legs must balance the load:
n x T x sin(theta) = W
so the per-leg tension is:
T = W / (n x sin(theta))
The angle factor is 1 / sin(theta), multiplied by the
vertical load share per leg.
Included angle mode assumes a symmetric bridle and converts the included angle at the hook into the same horizontal-angle basis: theta = 90 - A/2 For adjacent strength checks, use the wire rope stretch calculator, standing rigging wire size calculator, or bolt pattern force calculator.
Worked example
Verified against the live calculator
A 2,000 lbf load on 4 loaded legs at
60 deg from horizontal gives a vertical share of
500 lbf per leg. The angle factor is
1 / sin(60) = 1.155, so each leg carries about
577 lbf. With 1,500 lbf per-leg WLL,
total vertical capacity at that angle is about 5,196 lbf
and utilization is about 38.5%.
Frequently asked questions
How do you calculate sling angle tension?
For a symmetric load share, leg tension is T = W / (n x sin(theta)), where W is the total load, n is the number of loaded sling legs and theta is the sling angle from horizontal.
What does angle from horizontal mean?
A vertical sling leg is 90 degrees from horizontal and has an angle factor of 1. Lower sling angles increase leg tension because the vertical component of each leg gets smaller.
What is included angle mode?
Included angle mode is for the angle between opposite sling legs at the hook. The calculator assumes a symmetric bridle and converts included angle A into theta = 90 - A/2.
Can this approve a lift?
No. This is a geometry and utilization screen. Real rigging needs the actual sling tag or manufacturer table, hitch type, hardware, center of gravity, inspection condition and qualified review.
Method & assumptions
- The load is shared equally by the entered loaded-leg count.
- The sling angle is measured from horizontal; included-angle mode assumes symmetric opposite legs.
- The entered WLL is the applicable per-leg rated capacity for the sling type and hitch before this simple angle screen.
- Unequal sling lengths, off-center center of gravity, basket/choker reductions, D/d, edge protection, hardware, dynamic effects and inspection condition are not modeled.
- Use sling manufacturer data, qualified rigging review and current safety requirements for final lifting decisions.
- OSHA safe sling use guidance notes that rated loads depend on sling material, hitch, loading angle, D/d and fabrication details.