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Calcimator

Timber Frame Design Calculator

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

Inputs

ft
psf
ft
in
in

Results

Actual bending stress (fb)

864 psi

Bending demand/capacity ratio0.86
Bending check pass1
Required section modulus86.4 in³
Provided section modulus100 in³
Max deflection0.22 in
Deflection limit (L/240)0.6 in
Deflection demand/capacity0.37
Deflection check pass1
Uniform load on beam400 lb/ft
Max bending moment7,200 lb·ft
Moment of inertia (I)500 in⁴
How to Use This Calculator
  1. Enter Beam span, Total load (dead + live), and Tributary width.
  2. Set Beam width (b), Beam depth (d), and Wood species.
  3. Review the Actual bending stress (fb) (psi) result.
  4. Use Bending demand/capacity ratio and Bending check pass to inform your decision.

How the result changes with Beam depth (d)

Beam depth (d)Actual bending stress (fb)
5.42,963 psi
14441 psi
24150 psi
3379 psi

What each input means

Beam span
Clear span of the beam between supports.
Total load (dead + live)
Combined dead load + live load on the floor or roof (e.g., 40 live + 10 dead = 50 psf).
Tributary width
Half the bay spacing on each side of the beam. For a 16 ft bay, tributary width is 8 ft.
Beam width (b)
Actual width of the timber beam cross-section.
Beam depth (d)
Actual depth of the timber beam cross-section.
Wood species
0 = Douglas Fir-Larch, 1 = Southern Pine, 2 = Eastern White Pine, 3 = Red Oak, 4 = Western Red Cedar.

What each result means

Actual bending stress (fb)
Computed bending stress at midspan: fb = M/S.
Bending demand/capacity ratio
S_required / S_provided. Must be ≤ 1.0 to pass.
Bending check pass
1 = pass (ratio ≤ 1.0), 0 = fail.
Required section modulus
Minimum section modulus needed: S = M×12 / Fb.
Provided section modulus
Section modulus of chosen beam: S = b×d²/6.
Max deflection
Maximum midspan deflection under uniform load.
Deflection limit (L/240)
Allowable deflection per L/240 serviceability limit.
Deflection demand/capacity
Actual / allowable deflection. Must be ≤ 1.0 to pass.
Deflection check pass
1 = pass, 0 = fail.
Uniform load on beam
Load per linear foot: total_psf × tributary_width.
Max bending moment
M = wL²/8 for simply-supported beam.
Moment of inertia (I)
I = b×d³/12 for rectangular section.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Beam span = 12, Total load (dead + live) = 50, Tributary width = 8, Beam width (b) = 6 = 6 input(s) provided
  2. Calculate Actual bending stress
    Actual bending stress = (M_lbft * 12) / S_provided
    864 = 864
  3. Calculate Bending demand/capacity ratio
    Bending demand/capacity ratio = S_required / S_provided
    0.864 = 0.864
  4. Calculate Bending check pass
    Bending check pass
    1 = 1

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

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