Load Angle Factor Table
As the included angle between sling legs increases, the tension in each leg rises and the effective safe working load decreases. The tension factor is calculated as TF = 1 / cos(half the included angle).
| Included Angle | Angle from Vertical | Tension Factor | % of SWL |
|---|---|---|---|
| 0° | 0° | 1.00 | 100% |
| 30° | 15° | 1.04 | 96% |
| 60° | 30° | 1.16 | 86% |
| 90° | 45° | 1.41 | 71% |
| 120° | 60° | 2.00 | 50% |
UK Mode Factors (LEEA)
The Lifting Equipment Engineers Association (LEEA) publishes mode factors that simplify SWL calculations for common sling configurations. These are the factors most commonly tested in CPCS assessments.
| Configuration | Mode Factor |
|---|---|
| Single vertical | 1.0 |
| Choke hitch | 0.8 |
| Basket hitch | 2.0 |
| 2-leg sling, 0–90° included angle | 1.4 |
| 2-leg sling, 90–120° included angle | 1.0 |
| 3 or 4-leg sling, even load | 2.1 |
| 3 or 4-leg sling, uneven load | 1.4 |
Formulas
The key formulas for sling angle calculations are:
- Tension Factor (TF) = 1 / cos(θ / 2), where θ is the included angle
- Effective SWL = Single Leg SWL × Mode Factor
Warning: 120° Maximum Included Angle
Never use slings at included angles greater than 120°. At 120° the tension factor reaches 2.0, meaning each leg carries the full weight of the load. Beyond 120° the effective SWL drops below 50% and the risk of sling failure increases dramatically.
Sling Angle Calculator
Calculate tension factors and effective SWL for any sling angle and configuration.
