Short Run Pro - Manufacturer of metal parts, custom metal brackets and custom metal fabrication services provider.
  • Beam Deflection Calculator

    Beam Deflection Calculator

  • No bracket will remain perfectly straight under even the lightest load. Even if a feather were placed on a 1/2” steel plate, the plate would bend under the weight. The bending would, however, be too small to notice and the plate certainly wouldn't be in any danger of failing.

    This calculator uses engineering beam theory to predict the deflection of a bracket under a given amount of weight. This is not intended to be a perfect representation of the behavior of a bracket under a load. It is only a tool to help you get an “idea.” There are several assumptions and simplifications that have been applied. Whenever possible we tried to make these assumptions as a “worst case scenario.”

    • Assumptions:
    • 1) The bracket will be supporting the entire weight of the countertop. In most applications, the countertop is overhung, with the main body of granite being supported by a knee wall or cabinet. When this is the case, the rigidity of the granite provides extra support so that the bracket is only supporting a fraction of the overhung weight.
    • 2) The bracket is ungusseted. A gusset adds significant strength to a bracket, but makes the calculations much more complex. This calculator is not a good indicator of the strength of a gusseted bracket.
    • 3) The bracket has no holes in the top. Holes weaken the bracket slightly but this is nearly always a negligible difference.

    • 1) The bracket is treated as a cantilevered beam.   The difference between a bracket and a cantilevered beam is shown below. Because of this simplification, this calculator does not account for any bending that may take place on the vertical leg.
      Cantilever Bracket
      Using the Calculator:

      The calculator has 5 fields for you to fill in.
    • 1) Material. Choose Steel or Aluminum.
    • 2) Load. This is the amount of weight the bracket will be supporting. You can calculate the weight of your granite overhang using our Granite Calculator. If you are using multiple brackets to support your granite, divide the total weight by the number of brackets.
    • 3) Length. Length of the bracket's horizontal leg.
    • 4) Width. Width of the bracket's horizontal leg. This is usually 2 inches.
    • 5) Thickness. Thickness of the bracket material. A thicker bracket is much better at supporting heavier loads.


      The deflection indicates how far the furthest edge of the bracket will go down under the applied weight. There are 2 deflections calculated, depending on where the weight is.
    • 1) Distributed load. This is the value that is of concern in most applications. This is when the weight (entered in “Load” above) is spread out over the entire length of the bracket.
    • 2) Point load at end. This assumes that all of the weight (entered in “Load” above) is at the very tip of the bracket.
      Bracket Calculation


    Load:  pounds
    Length:  inches
    Width:  inches
    Thickness:  inches
    Short Run Pro provides this Beam Deflection Calculator as a service to website users. As previously stated there are assumptions and simplifications included in the calculations and therefore this service will not be able to calculate specific applications to exact accuracy. Calculations derived by use of this service may be used to determine deflection in general, but should not be relied upon in a user's specific application.
    Distributed Load:  inches
    Point Load at End:  inches

      Equations: The equations used in this calculator are given below.
      Distributed load deflection = Distributed load deflection

      Point load deflection = Point load deflection

    • E= Modulus of Elasticity (in pounds per square inch)
    • I= Moment of Inertia (in inches^4)
    • W= Load (in pounds)
    • l= The length of the bracket (in inchesxx)