Calculate tributary width, tributary area, area load, line load, total load, and support reactions. Use this tributary area calculator for beams, joists, rafters, girders, columns, posts, footings, floor loads, roof loads, and preliminary structural planning.
Beam tributary area:
The calculator adds left and right tributary widths, then multiplies by supported length.
Joist or rafter tributary area:
The calculator uses member spacing as the tributary width and multiplies it by supported length.
Column or post tributary area:
The calculator multiplies tributary length by tributary width to estimate the area carried by the support.
Load conversion:
The calculator converts PSF area load into PLF line load and total pounds carried by the member.
A tributary area calculator helps estimate how much floor, roof, wall, or deck area is carried by a beam, joist, rafter, post, column, or footing.
It can help compare tributary width, tributary area, total area load, line load, total pounds, support reactions, and load per member.
Your result shows estimated tributary width, tributary area, total load in PSF, line load in PLF, total load in pounds, load per member, and simple support reactions. These are simplified planning estimates only.
Tributary area is the portion of floor, roof, wall, or deck area that transfers load to a specific beam, joist, rafter, column, post, or footing.
Add the tributary width from each side of the beam, then multiply by the supported length. Usually each tributary width is half the distance to the next support or member.
Multiply the area load in PSF by the tributary width in feet. For example, 55 PSF over a 10-foot tributary width equals 550 PLF.
No. This calculator gives a simplified tributary estimate. Real load paths can change because of framing direction, openings, cantilevers, point loads, beams, walls, and structural connections.