Tributary Area Calculator

Find the tributary area a member carries from the surrounding framing. Pick a beam/girder or a column, enter the spacings (or bay sizes) around it, and the app gives the tributary width, the tributary area, and — if you add a floor load — the line load on the beam or the axial load on the column. It also shades the tributary region on a plan.

⭐ Free to use · Balance … EP

① What carries the load?

Member

Tributary width = half the distance to each adjacent parallel member. Enter 0 for a side with no slab/bay (edge or corner member).

② Beam / girder geometry

Member span L (m)

Spacing one side, s₁ (m)

Spacing other side, s₂ (m)

③ Load (optional — to get the member load)

Floor area load q (kPa)

Use a factored q (e.g. 1.2D + 1.6L) for a design load, or a service q. 1 kPa = 1 kN/m².

📐 Tributary result

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Tributary area

Results

Worked solution

⚠️ Tributary area is a load-path estimate. It splits load at the midpoint between members (the one-way / strip idealization). A genuine two-way slab sheds load triangularly/trapezoidally to its edge beams — use this as a first pass and confirm against your framing plan and the NSCP 2015.

Tributary Area Calculator

① What carries the load?

② Beam / girder geometry

② Surrounding bays (column)

③ Load (optional — to get the member load)

📐 Tributary result

Worked solution