Steel I-beams, so-named because they resemble an upper-case "I", are relied on in building projects for their strength and durability. Whenever you decide to take on a building project it is best to predict the strain that will be placed on your materials, as even steel has its limits when it comes to load. Fortunately there are tools that can help you decide on an acceptable weight for a steel I-beam.

I-Beam Depth

When you look at an I-beam from the end, there are parallel top and bottom flanges, and a thinner, perpendicular piece connecting them in the center. The total height of this section is referred to as the depth, and the depth is one of the key components of the beam's capacity. Generally speaking the greater the depth, the more of a load the beam can accept.

Weight Per Unit

The weight of a beam can also be measured in foot pounds per square foot. This measurement is the second part of the description of an I-beam. For instance, an I-beam that is described as S15X50 is a beam with a depth of 15 inches and a nominal weight per foot of 50 pounds. This also plays into capacity, as the weight per unit combined with the depth gives you a good measure of a particular beam.

Variables

There are a many variables as to how much a beam can hold. For instance, a load of 10 tons might easily be supported over the length of a beam, but if that load is all on one side of a beam, or narrowed so that weight is placed on a single inch of the beam, it changes things. Additionally beams can be reinforced by the number of support pillars that hold them up and by shims that are placed between the upper and lower flanges to increase support. You need to know how the beam is going to be supported and what the weight on it will be.

Calculators

There are a number of online programs that can help you calculate what your particular steel I-beams can hold. E Funda has a section that deals in the specifics of I-beams based on the depth and weight per unit measurements, and another section that helps give insight to the load on a beam based on where that load will be distributed.