W_adj = W × (1 + dynamic% / 100)
T = W_adj / (n × sin(θ)) when θ is from horizontalT = W_adj / (n × cos(θ)) when θ is from verticalV = T×sin(θ), H = T×cos(θ)V = T×cos(θ), H = T×sin(θ)Required WLL = T × safety factor
- Enter the load weight and choose the unit.
- Select the number of sling legs sharing the load.
- Measure the sling angle and choose the reference direction.
- Add a dynamic factor if the lift may jerk or sway.
- Set a safety factor to compute a conservative requirement.
- Optionally enter a leg rating to get a pass/fail check.
- Press Calculate. Download CSV or PDF if needed.
| Load (kg) | Legs | Angle (°) | Dynamic (%) | Safety | Est. Tension/Leg (kg) |
|---|---|---|---|---|---|
| 80 | 2 | 60 | 10 | 1.25 | ≈ 50.8 |
| 120 | 2 | 45 | 15 | 1.30 | ≈ 109.2 |
| 150 | 4 | 60 | 10 | 1.25 | ≈ 47.7 |
| 200 | 2 | 30 | 20 | 1.35 | ≈ 277.1 |
| 300 | 4 | 45 | 10 | 1.25 | ≈ 117.9 |
Angle Selection and Tension Behavior
In garden lifting, sling angle is the biggest driver of leg tension. When the angle is measured from horizontal, tension rises as the angle decreases because the vertical share per leg is proportional to sin(θ). At 60°, a two‑leg lift often stays close to the adjusted load per leg. At 30°, the same lift can exceed the load by a wide margin, especially with motion.
Leg Count and Load Sharing
More legs can reduce the theoretical tension, but only if the load is balanced and all legs are actually taking share. The calculator assumes equal sharing across the selected legs. For uneven loads such as soil bags, potted trees, or tool crates, real-world sharing may shift. Use conservative inputs and verify rigging symmetry before moving anything.
Dynamic Allowance for Starts and Stops
Garden lifts rarely stay perfectly steady. A small jerk when lifting a planter, a sudden stop, or wind on a tarp can increase effective load. The dynamic factor adds a percentage multiplier to the base load to represent these conditions. For careful hand-operated hoists, 5–10% may be reasonable. For quick lifts or sway, 15–25% is a safer planning range.
Safety Factor and Rating Checks
Working Load Limit per leg should exceed the calculated tension by a margin. This tool applies a safety factor to estimate a required leg rating. If you enter a rating, the PASS/FAIL status compares it against the requirement. A PASS means the entered rating meets the computed need under the selected assumptions, not that every on-site risk is eliminated.
Using Outputs for Practical Decisions
Use the vertical component to confirm that all legs together match the adjusted load, and use the horizontal component to understand inward pull on the load or attachment points. If tension is high, increase the sling angle, increase leg count only when sharing is reliable, reduce dynamic allowance by slowing the lift, or select higher-rated gear. Exporting CSV or PDF helps document the setup for repeat tasks.
Q: What angle should I use for safer lifting?
A: Higher angles generally reduce tension. If measured from horizontal, moving from 30° to 60° can dramatically lower leg load. Stay within your equipment guidance and keep the lift stable.
Q: Why does tension exceed the lifted load?
A: Because each leg is pulling at an angle, only part of its tension is vertical. The legs must generate enough vertical components to equal the adjusted load.
Q: What does the dynamic factor represent?
A: It models added force from starts, stops, sway, and minor impacts. Increasing it raises the adjusted load and tension, helping you plan conservatively for real handling conditions.
Q: Should I always use four legs instead of two?
A: Not automatically. Four legs can reduce tension if sharing is even, but uneven attachment points can overload one leg. Use balanced rigging and conservative assumptions.
Q: What if my angle is measured from vertical?
A: Select “Measured from vertical.” The calculator then uses cos(θ) for the vertical share. This keeps the math consistent with how you measured the angle.
Q: Is PASS a guarantee that lifting is safe?
A: No. PASS only indicates the entered rating meets the computed requirement using your inputs. Inspect gear, use proper attachment points, and follow manufacturer and site safety practices.