Skip to main content
Calcimator

Post and Beam Layout Calculator

Post spacing, post count, beam quantities, and post load capacity for rectangular post-and-beam structures.

Inputs

ft
ft
ft
psf
in

Results

Total posts

15

Max post load (interior)

6,000 lbs

≈ 6 grand pianos

Post axial capacity64,000 lbs
Post utilization ratio0.09
Min post size needed2.4 in
Bays along length4
Bays along width2
Actual bay spacing (length)10 ft
Actual bay spacing (width)12 ft
Total beam segments22
Total beam length240 LF
Building footprint960 sq ft
Beams Along Length3
Beams Along Width5
How to Use This Calculator
  1. Enter Building length, Building width, and Target bay spacing.
  2. Set Total floor/roof load, Post size (square), and Wood species.
  3. Review Total posts and Max post load (interior) (lbs).
  4. Use Post axial capacity (lbs) and Post utilization ratio to inform your decision.

How the result changes with Building width

Building widthTotal postsMax post load (interior)
27204,500 lbs
75405,357 lbs
133655,542 lbs
181855,656 lbs

What each input means

Building length
Overall building length along the long axis.
Building width
Overall building width along the short axis.
Target bay spacing
Desired distance between posts. Actual spacing may be adjusted to divide evenly.
Total floor/roof load
Combined dead + live load carried by the frame.
Post size (square)
Nominal square post dimension (e.g., 8 for an 8×8 post).
Wood species
0 = Douglas Fir-Larch, 1 = Southern Pine, 2 = Eastern White Pine, 3 = Red Oak.

What each result means

Total posts
Number of posts in the rectangular grid.
Max post load (interior)
Axial load on a fully-loaded interior post.
Post axial capacity
Compression capacity: A × Fc (short column).
Post utilization ratio
Load / capacity. Must be ≤ 1.0.
Min post size needed
Minimum square post side to carry the interior load.
Bays along length
Number of structural bays along the building length.
Bays along width
Number of structural bays along the building width.
Actual bay spacing (length)
Adjusted bay spacing to divide length evenly.
Actual bay spacing (width)
Adjusted bay spacing to divide width evenly.
Total beam segments
Number of individual beam segments in the grid.
Total beam length
Total linear feet of beams needed.
Building footprint
Length × width floor area.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Building length = 40, Building width = 24, Target bay spacing = 12, Total floor/roof load = 50 = 6 input(s) provided
  2. Calculate Total posts
    Total posts = postsAlongLength * postsAlongWidth
    15 = 15
  3. Calculate Max post load
    Max post load = maxTributaryArea * totalLoadPsf
    6000 = 6000
  4. Calculate Post axial capacity
    Post axial capacity = postArea * Fc
    64000 = 64000
  5. Calculate Post utilization ratio
    Post utilization ratio = interiorPostLoad / postCapacity
    0.094 = 0.094

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Timber Framing

Timber Frame Design Calculator

Beam sizing from span, load, and wood species using NDS bending and deflection checks.

Timber Framing

Timber Grade Selection Calculator

Compare 9 species/grade combinations for a beam application with bending and deflection checks.

Timber Framing

Timber Volume Calculator

Board feet, cubic volume, and weight from timber dimensions and species.

More in Construction & Building Trades.