The m ost important step in any rigging operation is determ ining the weight of the load to be hoisted.

This information can be obtained from shipping papers, design plans, catalogue data, manufacturer’s specifications, and other dependable sources. When such information is not available, it is necessary to calculate the load weight.

Let’s take steel as our example.

On erection plans, the size of steel beams is usually supplied together with their weight per length and the length of the member. Consequently it’s easy to compute the weight of any member to be lifted.

Where angle, plate, or built-up members are involved, however, the weights must be calculated. Memorizing one basic weight and two formulas will give the rigger a reasonably accurate estimate of weight.

The basic weight is that of 1 square foot of steel an inch thick – about 40 pounds. So two plates of steel each measuring 1 1/2” by 3’ by 6’ would weigh a total of


The weights of angles can also be figured with results close enough for safe job use. An angle is a structural shape which can be considered a bent plate with some additional metal at the centre for strength and a lesser amount of metal at the tips for ease of rolling. If the angle is flattened out, the result is a plate.

For example, a 5 by 3 by 1/4 inch angle would flatten out to approximately an 8 by 1/4 inch plate. This should weigh 40 pounds x 8/12 x 1/4 or 6.65 pounds per foot.






For other materials the weights are normally based on their weight per cubic foot, so you have to determine how many cubic feet of material (the volume) you are hoisting in order to estimate the weight.


For example, suppose you have a bundle of spruce lumber to hoist and the bundle is 12 ft. long, 3’ high and 4’ wide. (Fig. 1.3) The weight per cubic foot from Table 1.2 is 28 lbs., so the weight of this bundle is 12 x 3 x 4 x 28 = 4,032 Ibs.

The time taken to calculate the approximate weight of any object, whether steel, plates, columns, girders, castings, bedplates, etc., is time well spent and may save a serious accident through failure of lifting gear. The following tables of weights of various materials (Tables 1.1, 1.2, 1.3) should enable any rigger to compute the approximate weight of a given load. When in doubt, do not hesitate to seek advice from an engineer or foreman on the job.