Timber Grade Selection Calculator

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

Inputs

Beam span

ft

Total load

psf

Tributary width

ft

Beam width

in

Beam depth

in

Tab to move between fields

Results

Grades that pass

5

Max bending moment12,800 lb·ft

Section modulus provided144 in³

Uniform load on beam400 lb/ft

DF-L Select Struct. bending ratio0.67

DF-L Select Struct. defl. ratio0.45

DF-L Select Struct. pass1

DF-L No.1 bending ratio0.79

DF-L No.1 pass1

DF-L No.2 pass0

Southern Pine SS pass1

Southern Pine No.1 pass1

Southern Pine No.2 pass1

E. White Pine SS pass0

E. White Pine No.1 pass0

E. White Pine No.2 pass0

1

Your Inputs

Values entered

= Beam span = 16ft, Total load = 50psf, Tributary width = 8ft, Beam width = 6in, Beam depth = 12in

= 5 inputs provided

2

Formula

M = wL²/8 | f_b = M / S | Deflection = 5wL⁴/(384EI) | Utilization = f_b / F_b

= M = wL²/8 | f_b = M / S | Deflection = 5wL⁴/(384EI) | Utilization = f_b / F_b

= Applied to your values

3

Grades that pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 5

Number of the 9 species/grade combos that _pass both checks.

4

Max bending moment

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 12,800 lb·ft

M = wL²/8.

5

Section modulus provided

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 144 in³

S = bd²/6.

6

Uniform load on beam

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 400 lb/ft

w = load_psf × tributary_width.

7

DF-L Select Struct. bending ratio

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0.67

Bending demand/capacity for Douglas Fir-Larch Select Structural.

8

DF-L Select Struct. defl. ratio

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0.45

Deflection demand/capacity.

9

DF-L Select Struct. pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 1

1 = _pass, 0 = fail.

10

DF-L No.1 bending ratio

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0.79

Bending ratio for DF-L No.1.

11

DF-L No.1 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 1

1 = _pass, 0 = fail.

12

DF-L No.2 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0

1 = _pass, 0 = fail.

13

Southern Pine SS pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 1

1 = _pass, 0 = fail.

14

Southern Pine No.1 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 1

1 = _pass, 0 = fail.

15

Southern Pine No.2 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 1

1 = _pass, 0 = fail.

16

E. White Pine SS pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0

1 = _pass, 0 = fail.

17

E. White Pine No.1 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0

1 = _pass, 0 = fail.

18

E. White Pine No.2 pass

Calculated from your inputs

= Based on Beam span (16ft), Total load (50psf), Tributary width (8ft), Beam width (6in), and Beam depth (12in)

= 0

1 = _pass, 0 = fail.

How to Use This Calculator

Enter Beam span, Total load, and Tributary width.
Set Beam width and Beam depth.
Review the Grades that _pass result.
Use Max bending moment (lb·ft) and Section modulus provided (in³) to inform your decision.

How the result changes with Beam span

Beam span	Grades that pass
7.6	9
17	4
27	0
36	0

What each input means

Beam span: Clear span of the beam.
Total load: Combined dead + live load.
Tributary width: Tributary width for the beam.
Beam width: Width of the timber beam.
Beam depth: Depth of the timber beam.

What each result means

Grades that pass: Number of the 9 species/grade combos that _pass both checks.
Max bending moment: M = wL²/8.
Section modulus provided: S = bd²/6.
Uniform load on beam: w = load_psf × tributary_width.
DF-L Select Struct. bending ratio: Bending demand/capacity for Douglas Fir-Larch Select Structural.
DF-L Select Struct. defl. ratio: Deflection demand/capacity.
DF-L Select Struct. pass: 1 = _pass, 0 = fail.
DF-L No.1 bending ratio: Bending ratio for DF-L No.1.

How this is calculated

Formula

M = wL²/8 | f_b = M / S | Deflection = 5wL⁴/(384EI) | Utilization = f_b / F_b

Engine last updated July 26, 2026. Checked against 2 independently-derived tests — how we verify calculators.

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