How to use this calculator
- Enter the span. Use the clear simple span between supports.
- Set the beam build-up. Enter the actual ply width, ply count and actual LVL depth.
- Enter live and dead line loads. Use the uniform load on the beam in kN/m or lb/ft, not total load.
- Use product design values. Enter the adjusted E, Fb and Fv values for the LVL product and design basis.
- Check utilization and depth. Compare bending, shear and deflection utilization, then pick the next available LVL depth above the required depth.
How it works
This LVL beam calculator turns a common span-table problem into the same section-property checks used by the general beam deflection calculator and beam load capacity calculator, but with LVL plies, depth and uniform line loads entered directly.
For a built-up rectangular LVL, the total width is b = n · b_ply.
The section properties are:
I = b · d^3 / 12
S = b · d^2 / 6
The simply supported uniform-load checks are then:
M = w · L^2 / 8
V = w · L / 2
fb = M / S
fv = 1.5 · V / (b · d)
delta = 5 · w · L^4 / (384 · E · I)
Live-load deflection is compared with the live limit, such as L/360.
Live plus dead deflection is compared with the total-load limit, such as
L/240. The governing utilization is the highest of bending, shear,
live deflection and total deflection.
Worked example
Verified against the live calculator
Check a 12 ft simple span using two 1.75 in LVL plies at
11.875 in depth. Use 320 lb/ft live load and
120 lb/ft dead load, with E = 2.0 Mpsi,
Fb = 2.6 ksi and Fv = 0.285 ksi.
The total line load is 440 lb/ft. Maximum moment is
7,920 ft·lbf, maximum shear is 2,640 lbf, bending
stress is about 1.16 ksi, and max rectangular shear stress is about
0.095 ksi. Live deflection is 0.153 in versus an
L/360 limit of 0.400 in; total deflection is
0.210 in versus L/240 = 0.600 in. Governing
utilization is 0.44, controlled by bending stress.
Frequently asked questions
How do you calculate LVL beam size?
For this preliminary uniform-load check, the LVL is treated as a rectangular simple-span beam. Bending uses M = wL²/8 and fb = M/S, shear uses V = wL/2 and fv = 1.5V/(b·d), and deflection uses delta = 5wL⁴/(384EI). The required depth is the largest depth demanded by bending, shear, live deflection and total deflection.
Are the loads entered as total load or line load?
Enter line load along the beam: kN/m in SI or lb/ft in imperial. The calculator multiplies that by span internally to get total load, maximum shear and maximum moment.
What design values should I use for E, Fb and Fv?
Use the current manufacturer or code-approved values for the exact LVL product, then apply any project-required adjustment factors for duration, depth, wet service, temperature, lateral stability and other conditions. The defaults are only a starting example.
Does this account for multiple-ply fastening?
No. The math assumes all entered plies act together. Side-loaded or built-up LVL beams need a separate fastener schedule so load transfers into every ply.
Does this replace span tables or ForteWEB?
No. It is a transparent first-pass calculator for a simple uniform-load span. Manufacturer span tables or software are still needed for final product selection, point loads, reactions, bearing, holes, notches, bracing and code combinations.
Why can deflection govern before bending stress?
Deflection scales with span to the fourth power, while bending stress scales with span squared. Long spans can feel or perform poorly even when bending stress utilization is below 1.0.
Method & assumptions
- Simple-span beam with a uniform line load only. Point loads, multi-span continuity, cantilevers and tapered members are not included.
- LVL section is treated as a perfect rectangular built-up beam. Plies are assumed to act together; multiple-ply connection design is separate.
- The calculator uses elastic bending and rectangular shear formulas. It does not include shear deflection, vibration, bearing length, lateral-torsional stability, holes, notches, fire design or connection checks.
- Enter manufacturer/code-adjusted design values. Do not mix design values and code provisions from different editions or products.
- Use the section modulus calculator for custom rectangular/steel sections, or the square tube deflection calculator for HSS frame members.