How to use this calculator
- Enter the clear opening. Use the door, window or masonry opening width and the available bearing length on each side.
- Add tributary wall load. Enter wall area load and the wall height treated as loading the lintel.
- Add framing load. Enter any floor, roof, beam or framing line load delivered above the opening.
- Enter section values. Use actual section modulus, moment of inertia, shear area, E and allowable stresses for the trial lintel.
- Check utilization. Review bending, shear, deflection and bearing utilization and compare required S/I against the trial member.
How it works
This lintel size calculator treats the opening as a simply supported member. Clear opening plus half of each bearing length gives the effective simple span used for bending and deflection.
Wall load is converted from an area load to a line load: w_wall = q_wall x tributary height The total uniform line load is then: w = w_wall + floor/roof line load + lintel self-weight That is why searches for lintel size by opening width, span and load, or wall height belong on this page rather than a deck joist span screen.
Opening Width, Wall Height & Load Worksheet
Use this worksheet to translate field wording into the calculator inputs before choosing a trial steel, wood, LVL, masonry or concrete lintel section. The lintel size chart route gives the same opening-load screen as a quick reference, while the header size calculator route maps load-bearing wall opening language back to this worksheet. The page checks the entered member; it does not select a code-approved span-table size.
| Field question | Calculator input | Design read |
|---|---|---|
| What is the opening width? | Clear opening span | Sets the primary bending and deflection span before bearing is added. |
| How much wall is above the opening? | Wall tributary height | Multiplies the wall area load into the wall line load over the lintel. |
| How heavy is the supported wall? | Wall area load | Captures masonry veneer, framing, finish and other distributed wall weight. |
| Is a floor, roof or beam loading the header? | Floor/roof line load or centered point load | Adds framing load that is not captured by wall height alone. |
| How much support exists at each end? | Left/right bearing length and bearing width | Controls effective span and bearing pressure at the supports. |
| What member are you trying? | Section modulus, moment of inertia and shear area | Determines bending, deflection and shear capacity for the trial section. |
The simple-span checks use:
M = w x L^2 / 8 + P x L / 4
V = w x L / 2 + P / 2
f_b = M / S
delta = 5 x w x L^4 / (384 x E x I) + P x L^3 / (48 x E x I)
For adjacent structural checks, use the beam load capacity calculator, beam deflection calculator, LVL beam calculator and section modulus calculator.
Worked example
Verified against the live calculator
A 4 ft clear opening with 6 in bearing at each
end has an effective span of 4.5 ft. With an
8 ft tributary wall height at 40 psf, plus
300 lb/ft floor or roof line load and 20 lb/ft
lintel self-weight, the total line load is about 640 lb/ft.
A trial member with S = 1.5 in3, I = 3.0 in4,
E = 29 Mpsi, Fb = 22 ksi, Fv = 14 ksi
and 0.1 ksi allowable bearing stress screens at roughly
0.69 governing utilization. In this example, bearing
pressure controls before bending, shear or deflection.
Frequently asked questions
How do you calculate lintel size?
For a preliminary simple-span screen, convert the wall area load and tributary height into line load, add floor or roof line load and lintel self-weight, then check bending, shear, deflection and bearing against the entered section properties and allowable values.
Is the lintel span the same as the clear opening?
Not exactly. This calculator estimates effective span as clear opening plus half of the bearing length at each end, because reactions are assumed to act near the middle of the bearing zones.
How do opening width and wall height affect lintel size?
Opening width sets the span demand, while tributary wall height converts area load into line load above the lintel. Longer openings and taller/heavier tributary walls increase bending, shear, deflection and bearing demand.
Can this choose a steel angle lintel?
It can check a steel angle, channel or beam if you enter the section modulus, moment of inertia, shear area and allowable values for that section. It does not select a code-approved member from a table.
Does this work for masonry or concrete lintels?
Only as a first-pass elastic load screen. Reinforced masonry or concrete lintels need reinforcement, development length, cracking, shear detailing and code provisions that are outside this calculator.
Does this replace a structural engineer or building code table?
No. Openings in load-bearing walls are code- and project-sensitive. Use this calculator to understand loads and section demands, then verify final lintel size, bearing, bracing, connections and load combinations with the governing code or engineer.
Method & assumptions
- Simple-span service-load screen with uniform line load and an optional centered point load.
- Effective span is approximated as clear opening plus half of each bearing length.
- Loads are unfactored/service loads unless you intentionally enter factored values and compatible design stresses.
- Section modulus, moment of inertia, shear area, E and allowable stresses are entered values; the calculator does not look up a code-approved lintel table.
- Does not check load combinations, lateral-torsional buckling, local/web buckling, masonry arching, reinforcement, development length, cracking, fire rating, connections, uplift, seismic/wind detailing or permit requirements.