How sling capacity by hitch works
A sling tag gives a vertical rating, the most one sling can carry in a straight vertical hitch. Every other hitch starts from that number:
- Vertical: capacity equals the tagged rating.
- Choker: capacity = vertical rating × a choker factor below 1, because the choke squeezes the sling and lowers what it can carry. Enter the factor for your sling. This page starts at 0.8 as a typical figure, not a requirement.
- Basket: one sling cradles the load, so two parts carry it. Capacity = vertical rating × 2 × sin(angle from horizontal). At 90° that is double the rating, and it falls as the sling flattens.
- Bridle (multi-leg): capacity = vertical rating × legs carrying × sin(angle from horizontal).
- Load per leg = load ÷ (legs carrying × sin angle). Compare it with the most one leg may carry.
On a three- or four-leg bridle, common rigging practice counts only two legs as carrying the load unless you have verified that all of them share it. A rigid load can end up resting on two legs while the others only steady it. Angles are measured from horizontal, the same way as in the sling angle calculator.
This is the public statics rule in our own words. ASME B30.9 (slings) sets the real requirements, so confirm every figure against it, your sling's tag and the maker's data. Basket and bridle ratings also depend on how tightly the sling bends, which the tag or maker covers and this tool does not.
Worked example 1: basket hitch at 60°
A sling tagged 5,000 lb vertical is used in a basket at 60° from horizontal. Capacity = 5,000 × 2 × sin 60° = 5,000 × 2 × 0.8660 = 8,660 lb. For an 8,000 lb load, each part carries 8,000 ÷ 2 ÷ 0.8660 = 4,619 lb, under the 5,000 lb one leg may carry. At 45° the same basket is worth 5,000 × 2 × 0.7071 = 7,071 lb, and the 8,000 lb load is over it.
Worked example 2: four-leg bridle at 45°
Each leg is tagged 4,000 lb vertical and the legs sit at 45° from horizontal. Counting two legs, capacity = 4,000 × 2 × 0.7071 = 5,657 lb. A 9,000 lb load puts 9,000 ÷ 2 ÷ 0.7071 = 6,364 lb on each carrying leg, well over 4,000, so this rigging fails the check. Counting all four legs would show 11,314 lb, but that figure only holds if the lift is verified to share the load across all four.
These are original arithmetic examples, not exam questions.
Sling capacity questions
Do I multiply by four on a four-leg sling?
Not unless you have verified that all four legs share the load. The common rule counts two legs, so capacity = rating × 2 × sin angle. That is why a four-leg bridle often lifts no more than a two-leg one.
Why is my basket hitch not double the rating?
Because the two parts only double the rating when they hang straight up. As the angle from horizontal drops, sin angle falls and capacity falls with it. At 30° a basket is worth exactly one vertical rating.
Is the choker reduction always 80%?
No. Eighty percent is a typical figure, and the real value depends on the sling type and often the angle of the choke. Use the number from your sling's tag or maker, and enter it in the choker factor box.
Sling and hitch questions show up on the NCCCO written exams. For more on the angle side, read sling angles and rigging basics for the written exam.
Need the load weight to check against this capacity? The load weight calculator estimates it from shape and material.