🌲 Wood Beam Span Calculator
Check bending, shear, and deflection limits for simple wood beams using actual sizes, real species data, and uniform load inputs.
Calculation breakdown
| Species | Fb | E | Note |
|---|---|---|---|
| SPF No.2 | 875 psi | 1.4 Mpsi | Light duty framing |
| Douglas Fir-Larch No.2 | 900 psi | 1.6 Mpsi | Stiff and common |
| Southern Pine No.2 | 1100 psi | 1.4 Mpsi | Higher bending value |
| LVL 1.9E | 2600 psi | 1.9 Mpsi | Long-span engineered beam |
| Nominal | Actual | Area | Use |
|---|---|---|---|
| 2x6 | 1.5 x 5.5 | 8.25 in2 | Shed and shelf |
| 2x8 | 1.5 x 7.25 | 10.88 in2 | Short floor beam |
| 2x10 | 1.5 x 9.25 | 13.88 in2 | Deck and porch |
| 2x12 | 1.5 x 11.25 | 16.88 in2 | Longer simple spans |
| Use | Load | Ratio | Comment |
|---|---|---|---|
| Floor beam | 40 psf | L/360 | Common occupancy |
| Deck beam | 60 psf | L/360 | Outdoor live load |
| Roof beam | 20 psf | L/240 | Snow or roof service |
| Shelf beam | 20 psf | L/180 | Light storage use |
The length of a beam depends on several factors. Between them is the size of the lumber, the type of wood, the quality of the lumber and the weight that it must bear. The depth of a beam matters more than the width.
About heavy wooden beams, you commonly use a simple rule: at least 1 inch each foot of length, so at least 20-inch depth. But all this depends on the wood species and quality. For wooden beams you usually take a deep proportion of 1/18.
How to Choose the Right Length and Depth for Wooden Beams
Like this for 10-meter length the least depth will be 56 cm, if the distance between supports isn’t too big. For joists in homes the used lengths commonly range from 3 until 6 meters. Solid sawn wooden beam can reach 12 until 18 times its normal depth.
With engineered lumber as LVL or glulam you can go until 18 until 30 times the depth, and it works well for 6 until 12 meters or even more.
Use charts for lengths of rafters and joists are easy, if you understand the basic structural rules. Those charts give maximum lengths for common wood species as Douglas-fir, spruce-pine-fir, southern pine and hem-fir. Commonly they show the #2 grade for those species.
Calculator for wooden beam lengths are important for contractors, engineers and architects in construction. It helps to estimate the maximum safe length according to loads, wood type and beam sizes. By means of such tool you can check whether a particular beam of some size backs uniform linear load, comparing the involved and allowed shear and bending tension.
Single beam requires other calculations than continuous beam backed in several spots. Are other things that alters the maximum allowed length for particular lumber, for instance humidity, grade, type, load and use conditions. For instance, 4×10 No. 1 yellow cedar beam with elastic module of 1,400 pounds each square inch bears load.
For roof or floor with light load and L/240 allowed, you commonly lay 3-1/2″ x 11-7/8″ glulam or two 1-3/4″ x 11-7/8″ LVLs as 30-foot girder. For L/360 limit of floor deflection one must choose a bigger size. Always check the local building code or ask a legal structural engineer.
