When selecting beam sizes RAM Steel Beam Design investigates the acceptability of the deflections based on the limiting deflection valuesxe "Deflection" and span‑to‑deflection ratios, L/d, specified by the user. The user can specify the limits on the construction dead load deflection, the total dead load deflection, the live load deflection, and the total deflection. On a beam‑by‑beam basis, either of two deflection criteria, the default or the alternate, may be assigned to a member.

RAM Steel Beam Design first calculates the point at which the maximum total deflection occurs, then compares the deflection limitations against the other deflection values that occur at that point. For example, if the maximum total deflection occurs at, say 15', the values of the deflections for the construction dead load, total dead load, and live load at that point are determined and compared against the limitations, even though for unusual loading patterns their maximums may not necessarily occur at or near that same point.

All deflection calculations are based on unfactored loads.

The value calculated, shown, and used for the total deflection is the Net Total Deflection. It is the total deflection minus the specified camber, if any.

For cantilevers, the L/d ratio is calculated using twice the cantilever length.