Enter the glulam length (ft), the width (ft), and the thickness (ft) into the Glulam Weight Calculator. The calculator will evaluate the Glulam Weight.
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Glulam Weight Formula
The calculator uses one of two formulas depending on the mode you select.
Size and density mode:
W = (b * d / 144) * L * rho * N
From lb/ft mode:
W = w * L * N
- W = total weight (lb)
- b = beam width (in)
- d = beam depth (in)
- L = beam length (ft)
- rho = density of the glulam (lb/ft³)
- N = number of beams
- w = weight per linear foot (lb/ft)
The size and density mode converts your width and depth to feet, multiplies by length to get cubic feet per beam, then multiplies by density and quantity. The lb/ft mode skips the geometry and goes straight from a published or measured linear weight to a total. Pick a standard beam size from the dropdown to auto-fill width and depth, or type your own dimensions in inches, millimeters, or centimeters. Density defaults to 35 lb/ft³, which covers most softwood glulams, but you can override it with a custom value in lb/ft³ or kg/m³.
Reference Tables
Use these values as a sanity check on your inputs and results.
| Beam size (in) | Cross-section (in²) | lb/ft at 35 pcf | 20 ft beam (lb) |
|---|---|---|---|
| 3-1/8 × 9 | 28.1 | 6.8 | 137 |
| 3-1/8 × 12 | 37.5 | 9.1 | 182 |
| 3-1/2 × 11-7/8 | 41.6 | 10.1 | 202 |
| 5-1/8 × 12 | 61.5 | 15.0 | 299 |
| 5-1/8 × 15 | 76.9 | 18.7 | 374 |
| 6-3/4 × 18 | 121.5 | 29.5 | 591 |
| 8-3/4 × 24 | 210.0 | 51.0 | 1,021 |
| Glulam type | Density (lb/ft³) | Density (kg/m³) |
|---|---|---|
| Light softwood (spruce, pine) | 28 to 32 | 450 to 510 |
| Typical Douglas-fir / Southern pine | 34 to 36 | 545 to 580 |
| Dense softwood (GL30c, GL32c) | 37 to 39 | 590 to 625 |
| Hardwood glulam | 40 to 50 | 640 to 800 |
Example and FAQ
Example: You need the weight of two 5-1/8 in × 15 in glulam beams that span 24 ft, using 35 lb/ft³ density.
Cross-section area = 5.125 × 15 = 76.875 in² = 0.5339 ft². Weight per foot = 0.5339 × 35 = 18.69 lb/ft. Weight per beam = 18.69 × 24 = 448.5 lb. Total for two beams = 897 lb.
Why does the calculator ask for density?
Glulam is made from many wood species and adhesives. A 5-1/8 × 15 beam in light spruce weighs roughly 15 percent less than the same beam in dense Douglas-fir. Setting the right density keeps the estimate within a few percent of actual.
Does the weight include moisture?
The default densities assume the standard service moisture content of about 12 percent. Freshly manufactured or rain-soaked beams can weigh 5 to 15 percent more. Bump the density up if you are estimating shipping weight on green stock.
Can I enter fractional inches?
Yes. Type values like 3 1/2, 5-1/8, or 11 7/8 in the width and depth fields. The parser also accepts decimals.
What if I only know the weight per linear foot?
Switch to the "From lb/ft" tab and enter the published value. This skips the geometry and density step entirely and is the most accurate option when the manufacturer lists a linear weight.
