RigMaster How to determine the weight of a load before lifting it
Use the shipping papers, the nameplate or a load cell whenever you can. When you cannot, calculate volume × material density: a 10 × 4 × 1 ft steel plate is 40 ft³ × 490 lb/ft³ = 19,600 lb. RigMaster Pro's Load Weight Estimator does this for plates, round bars and pipe in 13 materials.
3 ways to determine the weight of a load
- Documents: shipping papers, bills of lading, drawings or the manufacturer's data.
- The load itself: a nameplate or a weight stencilled on it.
- Measure it: a load cell or dynamometer, or a calculation from dimensions and material when nothing else is available.
A calculation is the last resort, not a shortcut. We've also used it the other way around — a nameplate claimed a figure that looked too light for the size of the thing, and the formula backed us up, which was worth knowing before anyone picked it.
The formula
- Plate or block: volume = length × width × thickness.
- Round bar: volume = π × (diameter ÷ 2)² × length.
- Pipe or tube: volume = π × ((outer diameter ÷ 2)² − (inner diameter ÷ 2)²) × length.
- Weight = volume × density.
Worked examples
| Load | Volume | Weight | Tons / Tonnes |
|---|---|---|---|
| Steel plate 10 × 4 × 1 ft | 40.00 ft³ | 19,600 lb | 9.80 |
| Steel round bar Ø 2 ft × 10 ft | 31.42 ft³ | 15,394 lb | 7.70 |
| Steel pipe OD 2 ft, ID 1.5 ft, 10 ft | 13.74 ft³ | 6,735 lb | 3.37 |
| Concrete block 8 × 4 × 2 ft | 64.00 ft³ | 9,600 lb | 4.80 |
| Steel plate 3 × 1.2 × 0.3 m | 1.08 m³ | 8,477 kg | 8.48 |
| Concrete block 2 × 1 × 1 m | 2.00 m³ | 4,806 kg | 4.81 |
Tons are US short tons of 2,000 lb; in metric the app shows Tonnes of 1,000 kg.
Built-in material densities
| Material | lb/ft³ | kg/m³ |
|---|---|---|
| Steel | 490 | 7,849 |
| Stainless Steel | 494 | 7,913 |
| Cast Iron | 450 | 7,208 |
| Aluminum | 169 | 2,707 |
| Copper | 559 | 8,954 |
| Brass | 535 | 8,570 |
| Lead | 708 | 11,341 |
| Concrete | 150 | 2,403 |
| Sand (dry) | 100 | 1,602 |
| Gravel | 105 | 1,682 |
| Wood — Douglas Fir | 34 | 545 |
| Wood — Oak | 47 | 753 |
| Water | 62.4 | 1,000 |
Steps in RigMaster
- Open Load Weight Estimator from Pro Calculators.
- Under Shape & Material, pick the Shape: Rectangular / Plate, Cylinder / Round Bar or Pipe / Tube.
- Pick the Material; its density is shown in the list.
- Under Dimensions, fill in Length and then Width and Height / Thickness, or Diameter, or Outer Diameter and Inner Diameter.
- Read the Estimated Weight: Weight, Tons or Tonnes, and Volume.
- Carry the weight into Sling Tension or Hitch Capacity, or tap Save.
Common mistakes
- Inches typed as feet. Lengths are decimal feet or metres, so a 6 in plate is 0.5 ft thick. Typing 6 makes it twelve times heavier.
- Forgetting what is inside. A pipe full of water, a tank with residue or a crate with contents weighs far more than the shell.
- Assuming plain concrete. Reinforcing steel makes real concrete heavier than the 150 lb/ft³ in the table.
- Leaving out the rigging. Add the hook block, slings, shackles and any spreader to the load yourself; the estimator does not.
- Complex shapes. Only three shapes are available, so break a part into pieces and add them, and round up.
Questions and answers
How do you calculate the weight of a steel plate?
Length × width × thickness × 490 lb/ft³ for carbon steel. A 10 × 4 × 1 ft plate is 40 ft³ and 19,600 lb.
What is the weight of a steel pipe?
Take the outer area minus the inner area, times length, times density. A steel pipe with a 2 ft outside and 1.5 ft inside diameter, 10 ft long, comes to 6,735 lb empty.
Can I use the weight estimate for the lift?
Only as a cross-check or when no better figure exists, and then with margin. Documents, the nameplate or a load cell come first.
Is the Load Weight Estimator free?
No. It is part of the optional Pro upgrade.
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- Calculate sling angle from length and height
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- Short ton vs metric tonne: which one is heavier, and which one does RigMaster show?
- All questions about RigMaster
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