Rigging Capacity Calculator

Work out rigging capacity instantly with clear inputs, formula shown and shareable results.

About Rigging Capacity Calculator

The capacity of a multi-leg sling set is not simply the sum of the legs. The angle reduces each leg's vertical contribution by its sine, and on a four leg set only three legs are assumed to carry load because a rigid item rarely bears evenly on all four. A further factor covers unequal leg lengths and off-centre loads.

Formulas

Rigging capacity

Capacity = WLL per leg x effective legs x sin(angle) x unequal loading factor

Effective legs

Four leg sets are rated on three legs unless the load is genuinely flexible

Worked example

With the default values below, Rigging Capacity Calculator returns Effective rigging capacity of 4,157. Change any input above and every figure here is recalculated in your browser.

Inputs used

Working load limit per legminimum 1 kg: 2,000 kg
Number of legsminimum 1: 4
Sling angle from the horizontalaccepts 5–90 °: 60 °
Allowance for unequal loadingaccepts 0.1–1: 0.8

Results

Effective rigging capacity: 4,157 kg
Angle reduction factor: 0.8660
Legs assumed to share the load: 3.0
Capacity ignoring angle and sharing: 8,000 kg

Step by step

1Values used
2Rigging capacity
3Effective legs
4Effective rigging capacity= 4,157 kg
5Angle reduction factor= 0.8660
6Legs assumed to share the load= 3.0
7Capacity ignoring angle and sharing= 8,000 kg

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Sling selection and lift planning must follow the accessory manufacturer's tables and be carried out by a competent person.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Sling selection and lift planning must follow the accessory manufacturer's tables and be carried out by a competent person.

Frequently Asked Questions

How is the Rigging Capacity figure worked out?

Capacity = WLL per leg x effective legs x sin(angle) x unequal loading factor. The capacity of a multi-leg sling set is not simply the sum of the legs.

Why only three legs out of four?

A four leg set on a rigid load behaves like a table on an uneven floor: two diagonal legs take almost all the load. Rating on three is the standard conservative allowance.

What values do I need to enter?

This calculator takes 4 inputs: Working load limit per leg, Number of legs, Sling angle from the horizontal, Allowance for unequal loading. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.