Lift Inputs
Enter chart-based rated capacity for the planned radius and boom. This tool adds factors and checks utilization and ground bearing.
Formula used
- Total hook load (kg) = load + rigging + hook block + attachments.
- Dynamic factor depends on lift type (1.10, 1.25, 1.35).
- Wind force (N) = 0.613 × Cd × A × V², with V in m/s.
- Wind factor = 1 + min(0.10, wind force ÷ vertical force).
- Required rated capacity (kg) = total load × dynamic × wind × contingency ÷ (utilization limit).
- Sling leg tension (kg) = total load ÷ (legs × sin(angle)), angle from horizontal.
- Max outrigger reaction (N) = (total supported ÷ 4)×g + (hook load×g×radius) ÷ (2×span).
- Bearing pressure (kPa) = reaction ÷ pad area ÷ 1000.
How to use this calculator
- Pull the rated capacity from the correct crane chart entry.
- Enter load, rigging, hook block, and attachment weights.
- Set radius and boom length to match the planned geometry.
- Choose lift type and utilization limit for your policy margin.
- Add wind inputs for a conservative side load adjustment.
- Enter crane gross weight, outrigger span, pad area, and soil limit.
- Press Calculate and review capacity and ground checks.
- Export CSV or PDF to share the lift plan record.
Example data table
| Scenario | Hook load (kg) | Radius (m) | Rated capacity (kg) | Util limit (%) | Wind (km/h) | Soil allow (kPa) |
|---|---|---|---|---|---|---|
| Steel beam | 4,750 | 18 | 9,000 | 85 | 25 | 250 |
| HVAC module | 6,200 | 22 | 11,500 | 80 | 18 | 300 |
| Pipe spool | 2,100 | 12 | 7,500 | 85 | 30 | 200 |
Values are examples for demonstration only. Confirm with crane charts and site geotechnical data.
Professional guidance
Scope and lift inputs
This planner consolidates the key values normally scattered across lift plans: hook load components, working radius, boom length, chart capacity, and an operator-defined utilization limit. Recording the lift name, notes, and configuration keeps the calculation traceable during reviews. Enter weights in kilograms and geometry in meters so the resulting checks remain consistent across crews and subcontractors, with documented assumptions and consistent field units.
Capacity utilization and safety factors
The calculator converts “what is being lifted” into a required rated capacity by applying a lift-type dynamic factor and an optional contingency percentage. The utilization limit then enforces planning margin by reducing the allowable percentage of the chart value. This approach supports typical internal controls that cap lifts to a target band, such as 75–85%, while still allowing documented exceptions.
Wind side-load screening
Wind is treated as a horizontal load derived from exposed area, drag coefficient, and wind speed converted to meters per second. The tool compares this wind force to the vertical weight to produce a side-load ratio. When the ratio increases, the calculator applies a conservative wind factor so the required capacity rises. The warning flag highlights conditions where taglines, wind limits, or staging should be reconsidered.
Rigging leg tension visibility
Rigging selection often fails due to low sling angles. Using the number of legs and the angle from horizontal, the calculator estimates the tension per leg needed to support the total hook load. This output helps confirm sling and shackle working load limits, and it encourages better lift-point spacing or a different rigging arrangement when tensions escalate rapidly.
Ground bearing and outrigger pads
For setup validation, the tool estimates the maximum load-side outrigger reaction using crane gross weight, hook load, radius, and outrigger span. It converts the reaction into bearing pressure based on pad area and compares it with the soil allowable bearing value. The minimum pad area result provides an immediate sizing target, supporting safer selections when working on fill, pavement, or variable subgrade.
FAQs
1) Is this a substitute for the crane load chart?
No. Use the manufacturer chart as the source for rated capacity at the planned configuration. This tool adds planning factors and checks utilization and ground bearing based on your inputs.
2) What should I include in the total hook load?
Include the lifted item plus all below-hook accessories: slings, shackles, spreader bars, lifting beams, hooks, and any temporary attachments. If something moves with the load, count it.
3) How is wind handled in the calculation?
Wind force is estimated using exposed area, drag coefficient, and wind speed. The tool converts it to a side-load ratio and applies a conservative capacity increase, with warnings when side loading grows.
4) Why does sling tension increase at low angles?
As the sling angle from horizontal decreases, the vertical component of each leg drops. To carry the same weight, each leg must take higher tension. Verify rigging WLL at the computed leg tension.
5) What does the ground bearing check represent?
It estimates the maximum outrigger reaction and divides by your pad area to get bearing pressure. Compare it to allowable soil bearing from geotechnical guidance or site standards before setting outriggers.
6) What utilization limit should I choose?
Select a policy-based limit that builds margin into planning. Many organizations target 75–85% for routine lifts, lower for uncertain conditions. Document any deviation and apply additional controls if needed.