RigMaster How to calculate choker hitch and basket hitch capacity from the sling tag
Start from the vertical rated capacity on your sling's tag. A choker hitch is commonly rated at 75% of it, and a basket hitch at 2 × the rating × sin of the leg angle. A 2,000 lb sling gives 1,500 lb in a choker and 3,464 lb in a basket at 60°. RigMaster's free Hitch Capacity calculator applies these factors to your own tag rating.
Why the hitch changes what a sling can lift
The tag rating assumes a straight vertical pull, and a choker or basket is never that. In a choker the sling bends around itself at the choke point, which weakens it — you can see the crease on an old sling if you look. In a basket both ends go to the hook, so two parts share the load, but only fully when they hang straight down.
The capacity formulas
- Vertical: capacity = tag rating.
- Choker: capacity = 0.75 × tag rating.
- Basket: capacity = 2 × tag rating × sin(leg angle), with the angle measured from the horizontal.
Worked example: a sling tagged 2,000 lb vertical
| Hitch | Leg angle | Effective Capacity (lb) | Tag 1,000 kg |
|---|---|---|---|
| Vertical | - | 2,000 lb | 1,000 kg |
| Choker | - | 1,500 lb | 750 kg |
| Basket | 90° | 4,000 lb | 2,000 kg |
| Basket | 60° | 3,464 lb | 1,732 kg |
| Basket | 45° | 2,828 lb | 1,414 kg |
| Basket | 30° | 2,000 lb (caution) | 1,000 kg (caution) |
A basket at 30° is worth no more than a single vertical leg, and a basket below 30° falls under the red placard.
Steps in RigMaster
- Open Hitch Capacity from the Calculators list.
- Under Sling, type the Vertical Rating (tag WLL) printed on your sling's tag.
- Pick the Hitch: Vertical, Choker or Basket.
- For Basket, set the Leg Angle slider; the diagram and angle badge update as you drag.
- Read Effective Capacity, shown as Rated Capacity, and compare it with your load weight.
- Tap Save to keep the result in History.
Choker hitch capacity reduction: what 75% does not cover
The 75% figure assumes a normal choke angle. When the choke is pulled tighter, below about 120°, the capacity drops further. RigMaster does not calculate that extra reduction: it shows the note Standard 75% choker factor. A severe choke angle (< 120°) reduces capacity further — consult the sling chart. Check the manufacturer's chart for your sling type.
What the calculator doesn't know
- It has no sling tables at all. It never knows if you're using wire rope, chain or a synthetic round sling — it only uses the number you type off the tag, and that's on purpose.
- The basket formula ignores the D/d ratio, the bend diameter around the load or hook. Tight bends reduce basket capacity, especially on wire rope.
- Edge protection, temperature and sling condition never enter the calculation. A damaged or unreadable tag means the sling doesn't get used, full stop.
- Double chokers and double baskets use two slings; check each one against its own tag and the manufacturer's chart, not against half the result.
Questions and answers
What is choker hitch capacity?
What is the basket hitch capacity formula?
Does RigMaster have sling capacity charts?
Is the Hitch Capacity calculator free?
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