1) Why sling angle matters
For a given suspended load, a smaller sling angle increases leg tension. This calculator applies the common symmetric planning relationship, where each leg must provide a vertical component that sums to the effective load. As the angle from horizontal drops, the sine term drops, and tension rises quickly.
2) Typical tension multipliers
With a two-leg lift and a dynamic factor of 1.00, tension per leg equals W/(2·sinθ). At 60° from horizontal, sinθ≈0.866, so each leg carries about 0.577·W. At 45°, sinθ≈0.707, tension is about 0.707·W. At 30°, sinθ=0.5, tension becomes 1.00·W per leg.
3) Included angle and spread
Included angle is the angle between two sling legs. As it increases, each leg becomes more horizontal. For a quick reference, a 60° angle from horizontal corresponds to an included angle near 60° (two-leg bridle geometry). A 30° sling angle can push included angles toward 120°, where overload risk increases.
4) Dynamic factor and real lifts
Real picks often include start/stop motion, crane boom movement, or minor snatch. Using a dynamic factor like 1.10 to 1.30 can be a practical planning step. For example, a 2,000 load at 45° with D=1.10 produces about 1,556 tension per leg, matching the example table.
5) Capacity utilization checks
If you enter a rated leg capacity, the tool estimates utilization using allowable = rated divided by safety factor. This makes it easy to test alternatives: increase the angle, reduce the spread, add lift height, or use higher-capacity hardware. Treat utilization above 100% as a clear stop sign.
6) Geometry helper for field measurements
When the angle is unknown, measure rise (vertical height) and run (horizontal distance). The calculator converts these into an angle from horizontal using atan2(rise, run). This supports quick checks from tape measurements or lift sketches, especially during pre-task planning and toolbox talks.
7) Documentation and repeatability
Rigging decisions benefit from traceable records. Use the built-in CSV and PDF exports to store the input set, computed leg tension, and any warnings. Keeping a consistent record helps reviews, handoffs between crews, and quality audits for recurring lifts.
8) Important limitations
This calculator assumes symmetric load sharing across selected legs and does not model sling stretch, unequal angles, center-of-gravity offsets, or hardware geometry constraints. Always verify against manufacturer charts, site procedures, and a competent lift plan. When conditions are complex, use engineered rigging analysis.