Weight Estimation Procedure
Accurate load weight estimation is critical for safe lifting. Under LOLER 1998, the appointed person must determine the weight of the load before any lift. Follow these steps:
- Identify the load — determine the material, shape, and dimensions.
- Calculate the volume — use length × width × height (in metres) for rectangular loads, or the appropriate formula for the shape.
- Apply the material density — multiply volume by the density (kg/m³) from the reference table below.
- Add the weight of lifting accessories — include slings, shackles, beams, and any below-the-hook equipment.
- Apply a dynamic loading allowance — add 10–25% depending on conditions (see notes below).
- Compare against the crane's rated capacity — the total load must not exceed the crane's capacity at the required radius.
- Record in the lift plan — document the calculated weight and all assumptions.
Lifting Accessories — Typical Components
The total load includes everything suspended from the crane hook. Do not forget to include:
| Component | Notes |
|---|---|
| Load (primary item) | Calculated from dimensions and density |
| Hook block | Included in crane rated capacity on most modern cranes |
| Wire rope | Weight per metre varies by diameter; can be significant on long falls |
| Chain slings | Check the weight stamped on the identification tag |
| Shackles | Range from 1 kg to 50+ kg depending on SWL |
| Lifting beam / spreader bar | Weight marked on the beam; can be several hundred kg |
| Hoist rings / eyebolts | Usually minor but include in the calculation |
| Nets / bags / skips | Include the container weight (tare weight) |
Material Weight Reference
Use the following densities to estimate load weights. Where a range is given, use the higher value for safety.
| Material | Density (kg/m³) |
|---|---|
| Steel | 7,850 |
| Concrete (reinforced) | 2,400 |
| Timber (softwood) | 500–700 |
| Timber (hardwood) | 700–1,100 |
| Water | 1,000 |
| Soil (loose) | 1,200–1,500 |
| Sand (dry) | 1,500–1,700 |
| Gravel | 1,800–2,000 |
| Brickwork | 1,800–2,200 |
| Glass | 2,500 |
Dynamic Loading & Wind Allowance
Dynamic loading: Any sudden movement — such as snatching, swinging, or slewing — increases the forces on the crane and lifting accessories beyond the static weight. A minimum 10% allowance should be added for normal conditions. In adverse conditions (high wind, restricted visibility, complex lifts), increase this to 25%.
Wind creates additional horizontal forces on the load, especially on loads with a large sail area (e.g., sheet steel, cladding panels, containers). The appointed person must consider:
- Sail area of the load (m²)
- Current and forecast wind speed at working height
- Whether tag lines are required for load control
- Whether the lift should be postponed until conditions improve
Load Weight Calculator
Calculate total load weight including accessories and dynamic allowance.
