Chain Sling WLL (Grade & Angle) Calculator
Work out the Working Load Limit of a chain-sling arrangement from the single-leg WLL on the tag, the number of legs, and the sling angle. It applies the standard AS 3775 mode factors (measured from the vertical) so you get the true rated capacity for the way the sling is actually rigged.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the single-leg WLL printed on the chain sling's tag in kilograms — this already accounts for the chain grade (G80 / G100 / G120).
- Enter the number of legs sharing the load: 1, 2, 3, or 4.
- Enter the sling angle from the VERTICAL β in degrees (default 45). Measure from vertical, not from the horizontal — the two are easy to confuse.
- Read the mode factor, the arrangement WLL, and the angle band the calculator has used.
How it works
Arrangement WLL = single-leg WLL × mode factor M. The AS 3775 mode factors are: single leg M = 1.0; 2-leg M = 1.4 for 0–45° from vertical and 1.0 for 45–60°; 3- and 4-leg M = 2.1 for 0–45° and 1.5 for 45–60°. Angles beyond 60° from the vertical are not permitted because the leg tension rises steeply. The 3- and 4-leg factors assume a rigid load where, in practice, only three legs may take the full share.
Worked example
Worked example. A 2-leg chain sling is tagged WLL 2000 kg per leg and is rigged at 30° from the vertical. That falls in the 0–45° band, so the mode factor is 1.4 and the arrangement WLL = 2000 × 1.4 = 2800 kg. Open the legs out to 55° from vertical and the factor drops to 1.0, so the arrangement WLL falls to 2000 kg — the same as a single leg.
Common mistakes
- Measuring the angle from the horizontal instead of from the vertical — this calculator uses the angle from the vertical, as AS 3775 does.
- Trying to derive capacity from the chain grade — the grade is already baked into the tag WLL, so always use the tag value.
- Assuming all four legs of a 4-leg sling share equally — on a rigid load only three legs may carry the load, which is why the 3- and 4-leg factor is not simply double the 2-leg factor.
Frequently asked questions
Is the angle measured from the vertical or the horizontal?
From the vertical. β = 0° means the legs hang straight down; β = 60° is the widest permitted spread. Many riggers habitually think in included angle, so double-check before entering the value.
Why don't three and four legs give three or four times the capacity?
Because the load is rarely perfectly rigid and level, so it is not safe to assume every leg shares equally. The standard therefore rates 3- and 4-leg slings on the basis that only three legs may take the full load, giving factors of 2.1 and 1.5 rather than 3 or 4.
What happens beyond 60° from the vertical?
It is not permitted for standard slinging. As the legs open out, the tension in each leg climbs sharply for the same vertical load, so the standards cap the working angle at 60° from the vertical and this calculator returns an error above it.
Related tools
- Wire Rope SWL / Load Checker
- WLL from Breaking Load & Safety Factor Calculator
- Sling Angle Load Factor Calculator
- Sling D/d Ratio Efficiency Calculator
- Sling Length for Angle Calculator
- Two-Leg Sling Load Share Calculator
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