Calculator Inputs
Formula Used
This tool estimates allowable load from an effective rated moment, then subtracts accessory weights. It is intended for planning checks only and does not replace the manufacturer load chart.
- EffectiveMoment = RatedMoment × SetupFactor × WindFactor × SlewFactor × BoomFactor
- GrossCapacity = EffectiveMoment ÷ (Radius × DynamicFactor)
- NetCapacity = max(0, GrossCapacity − (HookWeight + RiggingWeight))
- Utilization% = IntendedLoad ÷ NetCapacity × 100
Always verify: configuration, counterweight, jib, reeving, outrigger spread, ground bearing, and wind limits per the approved lift plan.
How to Use This Calculator
- Enter the working radius and the chart-rated moment for the planned configuration.
- Select the load unit and provide hook block, rigging, and intended load values.
- Choose setup and slew position, then enter a realistic dynamic factor.
- Add wind speed to apply a conservative wind factor for planning checks.
- Optional: enter boom length and reference length to apply a mild boom factor.
- Press Calculate. Review net capacity, utilization, and the pass/fail indicator.
- Use CSV/PDF downloads for documentation, then validate with the load chart.
Example Data Table
| Radius (m) | Rated moment (kN·m) | Setup | Wind (m/s) | Dynamic | Net capacity (t) | Utilization (for 8t) |
|---|---|---|---|---|---|---|
| 10 | 1200 | Full outriggers | 6 | 1.10 | 10.10 | 79% |
| 12 | 1200 | Full outriggers | 6 | 1.10 | 8.27 | 97% |
| 14 | 1200 | Partial outriggers | 10 | 1.15 | 5.39 | 148% |
| 16 | 1400 | Full outriggers | 12 | 1.10 | 6.06 | 132% |
| 18 | 1600 | On tyres | 8 | 1.20 | 3.59 | 223% |
Example values are illustrative. Do not rely on them for real lifts.
Professional Guidance for Radius Capacity Checks
Crane lifting performance is controlled by two practical limits: structural strength and stability. In day-to-day planning, both limits are expressed through a rated moment at a stated configuration. This calculator uses that rated moment with your working radius to estimate a gross allowable load, then deducts hook block and rigging to display a net capacity you can compare with your intended load. It is designed for quick checks during lift preparation, method statements, and toolbox talks.
Radius is often the most sensitive input. A small increase in radius can reduce capacity sharply because the overturning moment grows in direct proportion to the horizontal distance. To keep decisions realistic, this tool applies planning factors that commonly affect usable capacity on site: setup condition (outriggers or tyres), slew position (front/side/rear), wind conditions, dynamic effects, and an optional boom factor. These factors are intentionally conservative and should support safer planning, not replace the manufacturer load chart or engineered lift plan approvals.
Example (illustrative): assume a 12 m radius, rated moment of 1200 kN·m, full outriggers, wind 6 m/s, and a dynamic factor of 1.10. Enter hook weight 1.2 t and rigging 0.8 t with an intended 8 t load. The calculator estimates a net capacity close to the example table (about 8.27 t) and a utilization near 97%. That indicates the lift is very close to the planning limit; in practice you would reduce radius, reduce accessory weight, or select a higher-rated configuration to restore margin.
Use the utilization figure as a communication tool. When utilization exceeds 100%, the lift is outside the estimated net capacity and should be redesigned. When utilization is near 90–100%, treat it as a prompt to refine the plan: verify the true radius at pick and set, confirm reeving and parts of line, confirm counterweight, validate ground bearing pressure, confirm wind limits for the load surface area, and check travel restrictions. Export the CSV or PDF to capture assumptions and provide a traceable planning record for supervisors and permit reviewers.
Rated moment must come from the correct load chart line for your exact configuration. Confirm boom length and angle, main boom versus jib, counterweight, outrigger spread, and duty rating. Where charts provide separate values for “over front” and “over side,” select the limiting direction for your pick and set. If the lift involves multiple radii during slewing or walking, use the worst-case radius and re-check the plan for each step.
Final reminder: always follow the approved lifting procedure and the crane manufacturer documentation. If any parameter is uncertain, perform a detailed lift study before executing the lift.
FAQs
1) What does “net capacity” mean in this tool?
Net capacity is the remaining allowable lifted load after subtracting hook block and rigging from the gross capacity. It helps you compare the intended load with a more realistic on-hook allowance.
2) Why does capacity drop quickly when radius increases?
Because overturning moment increases directly with radius. For a fixed rated moment, allowable load equals moment divided by radius, so small radius increases can significantly reduce permissible load.
3) How should I choose the dynamic factor?
Use higher values for fast hoisting, snatch, wind-induced sway, or poor control. Typical planning ranges are 1.05 to 1.30. If your procedure specifies a factor, use that value.
4) Does the wind factor replace wind limits in the load chart?
No. The wind factor is a conservative planning adjustment only. Always comply with the crane and rigging wind limits, consider load surface area, and stop operations when conditions exceed the approved plan.
5) Can I use tonnes or kN for weights?
Yes. Select the load unit once, then enter hook, rigging, and intended load in that unit. The tool converts internally to keep calculations consistent and shows both tonnes and kN in results.
6) What should I do if utilization is close to 100%?
Treat it as a warning to regain margin. Reduce radius, reduce rigging weight, improve setup, or select a higher-rated configuration. Then verify the final decision against the manufacturer chart and lift study requirements.
7) Is this calculator suitable for critical lifts?
Use it for preliminary checks and documentation. Critical lifts require a detailed engineered plan, verification against the exact load chart and configuration, and approval by competent personnel per your site procedures.