Calculate glulam beam weight from width, depth, length, and density, or solve for required length with imperial and metric units, quantity, and density presets.
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Glulam Weight Formula
The calculator uses one of two formulas depending on the mode you select.
Size and density mode:
From lb/ft mode:
- 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 dimensional modes use actual width, depth, density, and beam count to estimate total mass or solve for equal length per beam. The linear-weight mode uses a manufacturer-supplied weight per foot or meter. Enter dimensions as decimals; 5-1/8 inches is 5.125 inches. Density presets are estimates, not species or strength-grade specifications. Rosboro uses a 35 pcf weight assumption in its guide; use the density for your specific product.
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 |
| Illustrative higher-density softwood | 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 = 0.5338541667 ft². Weight per foot = 18.6848958333 lb/ft. Each 24 ft beam weighs 448.4375 lb; two total 896.875 lb (about 897 lb). The calculator keeps unrounded values through the calculation.
Why does the calculator ask for density?
Density depends on the specific product, wood species, moisture and treatment. The table gives illustrative ranges and does not establish a product specification or accuracy guarantee. Obtain density or linear weight from the manufacturer.
Does the weight include moisture?
The calculator applies the density you select without a moisture correction. Moisture and treatment can change weight. Use product-specific information for shipping or lifting; do not infer a fixed moisture percentage or weight increase from the presets.
Can I enter fractional inches?
Convert fractional inches to decimals before entry: 3 1/2 = 3.5, 5-1/8 = 5.125, and 11 7/8 = 11.875.
What if I only know the weight per linear foot?
Select “Total weight from linear weight” 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.
