LVL Beam Load Calculator: Span, Bending & Deflection

LVL Beam Load Calculator

Estimate the allowable uniform load a laminated veneer lumber beam can carry over a simple span, checking both bending stress and deflection limits, then compare it against an applied load for utilization and actual sag.

📌Real LVL Beam Presets

📝Beam Inputs

Beam depth (section)

Beam depth d (in)

Auto-filled by the size list; edit for a custom depth.

Ply count

Width per ply b (in)

Standard LVL ply is 1.75 in; 1.5 in stock also exists.

Clear span (ft)

Allowable bending Fb (psi)

Modulus of elasticity E (psi)

Deflection limit

Applied uniform load (plf, optional)

Total load per foot on the beam; leave 0 to skip utilization.

Shear value Fv (psi)

Allowable load 0 plf governing uniform capacity

Governing mode – bending vs deflection

Deflection at applied 0 in actual sag vs limit

Utilization 0% applied / allowable

🔢Section Snapshot

1.75Total width b (in)

0Section mod S (in³)

0Moment inertia I (in⁴)

0Max moment (ft·lb)

📏LVL Section Properties (1.75 in Ply)

Nominal Size	Area (in²)	S (in³)	I (in⁴)	Weight (plf)
1.75 × 7.25	12.7	15.3	55.6	3.5
1.75 × 9.25	16.2	24.9	115.4	4.5
1.75 × 9.5	16.6	26.3	125.0	4.6
1.75 × 11.25	19.7	36.9	207.6	5.5
1.75 × 11.875	20.8	41.1	244.1	5.8
1.75 × 14	24.5	57.2	400.5	6.8
1.75 × 16	28.0	74.7	597.3	7.8
1.75 × 18	31.5	94.5	850.5	8.8

Values for a single 1.75 in ply. Multiply Area, S, and I by the ply count for built-up beams; depth stays the same.

🧪Design Values by LVL Grade

Grade / Class	Fb (psi)	E (psi)	Fv (psi)	Typical Use
1.8E economy	2600	1,800,000	285	Headers, short spans
1.9E standard	2800	1,900,000	285	Floors, general beams
2.0E premium	2950	2,000,000	290	Long spans, garages
2.1E high grade	3100	2,100,000	300	Ridge, deep beams
Repetitive Fb boost	+4%	same	same	Closely spaced members

Design values vary by manufacturer and duration factor. Always confirm with the stamped product literature.

📊Deflection Limit Reference

Limit	Applies To	Sag at 12 ft	Sag at 18 ft	Sag at 24 ft
L / 480	Stiff floors, tile	0.30 in	0.45 in	0.60 in
L / 360	Floor live load	0.40 in	0.60 in	0.80 in
L / 240	Total load, roof	0.60 in	0.90 in	1.20 in
L / 180	Rafters, ceilings	0.80 in	1.20 in	1.60 in

Allowable sag = span (in) ÷ the limit denominator. Long spans hit these limits before bending stress does.

🗂Beam Size vs Span Comparison

Beam Build	Span (ft)	Allowable (plf)	Governs	Sag Limit	Sag at Allow
1.75 × 9.25 single	10	325	Deflection	L/360	0.33 in
1.75 × 9.25 single	14	118	Deflection	L/360	0.47 in
1.75 × 11.25 double	16	285	Deflection	L/360	0.53 in
1.75 × 11.875 single	12	398	Deflection	L/360	0.40 in
1.75 × 14 single	20	141	Deflection	L/360	0.67 in
1.75 × 14 double	20	282	Deflection	L/360	0.67 in
1.75 × 16 triple	18	1291	Bending	L/240	0.90 in
1.75 × 16 double	24	243	Deflection	L/360	0.80 in
1.75 × 18 triple	24	520	Deflection	L/360	0.80 in

Estimates use Fb 2800 psi and E 1.9×10⁶ psi. Notice deflection governs most open spans while short deep beams can be limited by bending.

⚙Full Formula Breakdown

Total widthb = ply count × width per ply. Three 1.75 in plies give b = 5.25 in.

Moment of inertiaI = b × d³ / 12. Depth is cubed, so deeper beams gain stiffness fast.

Section modulusS = b × d² / 6. This controls the bending stress capacity of the section.

Max momentFor a uniform load, M = w × L² / 8, with w in lb/in and L the span in inches.

Bending capacitySet M / S = Fb, giving allowable w_bend = 8 × Fb × S / L² (lb/in).

Deflection capacitySag δ = 5wL⁴ / (384EI). Solve at δ = L / limit: w_defl = 384 × E × I × δ / (5 × L⁴).

Governing loadAllowable w = min(w_bend, w_defl). Multiply lb/in by 12 to report plf.

UtilizationUtilization = applied load ÷ allowable load; actual sag scales with the applied w.

💡Practical LVL Tips

Deflection tip: On open spans past about 14 ft, the L/360 or L/240 sag limit almost always governs before bending stress does, so adding depth helps far more than a higher Fb grade.

Verification tip: This is an educational estimate for uniform loads only. Confirm point loads, bearing, shear, and lateral bracing with the manufacturer span tables and a licensed engineer.

Important: Results assume a simply supported beam with a single uniform load and do not include load duration factors, wet-service adjustments, concentrated loads, bearing checks, or lateral stability. Do not use these numbers for permitted construction without review by a qualified structural engineer.

There’s a wall there now, but you want open space. You’re standing in that empty room. The roof hangs overhead and gravity pulls down. How do you get something strong enough to keep it up? A common solution is laminated veneer lumber, which are both strong and predictable. Selecting the proper size comes down to weighing the stress of bending versus limiting deflection, and that’s what this calculator will do for you.

Then you can go back to thinking about other parts off the big picture: your renovation. The other concern most homeowners have with the beam is whether or not it will snap under the weight of roof and floors. Fair enough, but that’s not usually how a beam fail in your home. A beam in a long span doesn’t break all at once. It sags; too much. And yes, you may not notice a quarter-inch droop of sag initialy, but over time, that bow results in cracks forming in your drywall above. It’ll also cause your floors to feel bouncy and unsetteld to those who walk on them.

How to Pick the Right Beam Size

Deflection limits keep that from happening. One common deflection limit for residential building is L/360, which means a beam can sags no more than one three-hundred-sixtieth of its span length under live loads. This ensures the house doesn’t feel like a trampoline, it feels solid.

As it gets wider, it doesn’t get much stiffer, certainly not as much than it does when it gets taller. If we’re talking about volume, that makes no sense, yet in the math world, taller is better. For example: Double the depth of your beam, and it increases its resistance to bending by a factor of eight. Double the width? It’s now twice as strong. So even though an LVL beam is narrow and tall rather than wide and short (it gets it).

The calculator knows this, so as you tweak the number of plies and the depth, the relationship are accounted for. To add width, just stack them up (side by side) to increase bearing and shear. But getting deeper is much more effective at combating sag. This geometric effect would of saved you from having to purchase too much lumber to make code.

Stress under load is still important, particularly for short spans or heavily loaded span. This is where the allowable bending stress come into play. For normal grade lumber, it’s about 2800 psi, and the calculator check if your inputs exceed that. In other words, before it reaches its deflection limit, it may reach its stress limit… Which could occur when supporting multiple heavy floors or a masonry fireplace. While not common in most houses, it does apply to large commercial spaces and garages.

The tool will tell you what your constraints are (i.e., whether you need to worry more about strength or stiffness), so that you can make informed tradeoffs if you are limited by space. Note that these aren’t set figures that mean any build is OK or not. They are a good starting point if you want to design something, but reality makes it more complicated. Length of bearing supports must be sufficient. Lateral bracing prevents buckling. Permanent loads vs temporary loads has different load duration factors. All those things factor in when a qualified engineer make the decision.

The calculator helps to rule out possibilities and also helps explain the reasoning for choosing one over the other. Instead of hoping it’s built strong, you now have some concrete information (no pun intended) that you can bring to an expert who will confirm or deny it. Knowing how it works give you peace of mind.

You don’t want to build the strongest beam, you just need to build the right one. Too much and it’s a waste of money and headroom. Too little and it risks damage and safety issue. Too much and it wastes headroom and money. The trick is finding the balance between how much stress the wood can handle and how much sag your family can live with.

When those two lines cross, then the beam blends into the background. It’s there for support but doesn’t draw attention to itself. That’s good engineering. Everything sits on it and yet it’s out of sight. You’re not thinking about the support anymore, you’re livig in the space.