Calculator Form
Enter manufacturer chart values first. Then apply practical deductions for site planning.
Example Data Table
These examples show how varying setup and deductions affect usable capacity.
| Scenario | Rated Capacity (t) | Gross Load (t) | Radius (m) | Recommended Capacity (t) | Utilization (%) | Status |
|---|---|---|---|---|---|---|
| Rooftop HVAC Unit | 18.00 | 12.00 | 14.00 | 13.82 | 93.80 | Critical - near limit |
| Precast Wall Panel | 42.00 | 26.70 | 18.00 | 32.90 | 89.28 | Caution - review plan |
| Steel Truss | 30.00 | 19.00 | 20.00 | 19.92 | 106.80 | Overload - do not lift |
| Generator Set | 55.00 | 34.50 | 16.00 | 47.54 | 76.93 | Caution - review plan |
Formula Used
1. Gross lifted load
Gross Load = Load Weight + Rigging Weight + Hook Block Weight
2. Configuration capacity
Configuration Capacity = Rated Chart Capacity × Configuration Factor
3. Weather adjusted capacity
Weather Adjusted Capacity = Configuration Capacity × (1 − Wind Deduction ÷ 100)
4. Site adjusted capacity
Site Adjusted Capacity = Weather Adjusted Capacity × (1 − Site Reduction ÷ 100)
5. Recommended allowable capacity
Recommended Capacity = Site Adjusted Capacity × (Allowable Usage ÷ 100)
6. Effective demand
Effective Demand = Gross Load × Dynamic Factor
7. Utilization
Utilization % = (Effective Demand ÷ Recommended Capacity) × 100
8. Load moment
Moment = Load × Radius
9. Simple boom geometry checks
Tip Height = Boom Length × sin(Angle), Horizontal Reach = Boom Length × cos(Angle)
Use this logic for planning only. Final approval must always follow the exact manufacturer chart, operating procedure, and lift plan.
How to Use This Calculator
- Read the crane chart and enter the rated capacity for the exact planned radius and boom setup.
- Enter the load weight plus all below-hook items, including rigging and hook block.
- Set the load radius, boom length, boom angle, and parts of line for your expected configuration.
- Apply deductions for configuration, wind, and site complexity.
- Set an allowable usage target, then calculate the result.
- Review utilization, safety margin, line pull, and geometry notes.
- Compare the outcome with the official lift plan before work begins.
FAQs
1. What is crane lift capacity?
It is the maximum load a crane may lift at a specific radius, boom length, and configuration. Capacity changes with setup, attachments, wind, and operating method. Always begin with the manufacturer chart.
2. Why must rigging and hook block be included?
The crane lifts the full suspended mass, not only the object. Slings, shackles, spreaders, blocks, and other below-hook gear all consume capacity and increase the load moment.
3. Why does load radius matter so much?
A larger radius increases overturning moment. As the hook moves farther from the crane center, the safe lifting capacity usually drops quickly, even if the object weight stays unchanged.
4. What does the dynamic factor represent?
It accounts for motion effects such as starting, stopping, swinging, booming, and imperfect handling. Dynamic actions can make the effective demand higher than the static suspended weight.
5. Why apply wind and site deductions?
Wind, restricted space, uneven access, travel, and complex picks reduce practical operating comfort. Planning deductions help keep a margin before the lift reaches the chart limit.
6. Can this replace the manufacturer load chart?
No. This calculator is a planning aid. Final lift acceptance must follow the exact crane chart, setup conditions, accessory approvals, operating manual, and qualified lift supervision.
7. What utilization target is usually comfortable?
Many planners prefer a practical operating margin instead of working at the full adjusted limit. The right target depends on project rules, lift complexity, wind exposure, and engineering review.
8. Why compare boom geometry with the entered radius?
It is a quick consistency check. If the simple horizontal reach differs greatly from the entered radius, the selected boom angle, boom length, or pickup geometry may need review.