Door Header Size Calculator | IRC Span Chart
Free door header size calculator using IRC Table R602.7(1) spans. Enter the opening width and load-bearing status to get the header, from a double 2x4 to a quadruple 2x12.
Door Header Size Calculator
Valid range: 12-144 inches
Valid range: 24-120 inches
Recommended Header Size
The recommended header size is based on the door width and whether the wall is load bearing. For load-bearing walls, this assumes moderate conditions per IRC Table R602.7(1) (one floor plus roof/ceiling bearing on the header, a 28 ft building width, and 50 psf ground snow load). Wider buildings, additional floors bearing on the header, or higher snow loads require a larger header -- verify with a local code official or engineer for your actual conditions.
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Documentation
Door Header Size Calculator
A door header size calculator recommends the size of the horizontal beam, called a header, needed above a door opening. It uses the opening width and whether the wall carries structural load, then returns a size such as "Double 2x10" or "Single flat 2x4".
What is a door header?
A door header, also called a lintel, is a horizontal beam placed above a door opening. It carries the weight of the wall, ceiling, and sometimes the roof above the opening, and passes that weight down to the studs on either side of the door. Without a header, cutting a doorway into a wall would remove the wood that was holding up everything above it.
A header rests on jack studs, shorter studs cut to fit under each end of the header. Full-height king studs run alongside the jack studs from floor to top plate. Short cripple studs fill the gap between the top of the header and the top plate above.
A "double" or "triple" header means two or three pieces of lumber nailed face to face. The extra plies add thickness through the wall, so the beam gets stronger without getting deeper. A double 2x10 and a triple 2x10 are both 9.25 inches deep.
How to calculate door header size
Header size depends mainly on two things: the width of the opening and whether the wall is load-bearing.
A load-bearing wall holds up weight from the floor or roof above it. A non-load-bearing wall, sometimes called a partition wall, only holds up itself.
For non-load-bearing walls, the International Residential Code (IRC), section R602.7.3, allows a single flat 2x4 above any opening up to 8 feet (96 inches) wide. "Flat" means the 2x4 lies on its wide face instead of standing on edge.
For load-bearing walls, the required size comes from IRC Table R602.7(1), which lists the longest span each lumber size and ply count can carry. The tabulated span shrinks as the load grows: more floors bearing on the header, a wider building, or a heavier ground snow load all shorten it.
Wider openings need bigger headers because of basic beam mechanics. For a beam carrying a uniform load, the maximum bending moment is M = wLĀ²/8, where w is the load per inch of span and L is the span length. Because L is squared, doubling the span more than doubles the bending force the header must resist.
The load this calculator assumes
The calculator asks only for width, height, and the load-bearing checkbox, so it has to assume the rest. Height (24 to 120 inches) only scales the drawing; the header size comes from the width. It uses a middle-of-the-table row of IRC Table R602.7(1): the header supports the roof, the ceiling, and one center-bearing floor, the building is 28 feet wide, and the ground snow load is 50 pounds per square foot.
That is not the lightest tabulated case, and it is not the heaviest. A two-story house on a 36-foot footprint in heavy-snow country needs a larger header than the calculator shows. A single-story house on a 20-foot footprint with a 30 psf snow load can use a smaller one. A builder should confirm the exact table row with a local building department or a structural engineer before framing.
Within that assumption, the calculator walks the tabulated members from the smallest up (two-ply 2x4 through 2x12, then three-ply, then four-ply) and returns the first one whose allowable span is at least the opening width.
Door header size chart
Spans below are the tabulated values for the assumed load described above. The tool accepts widths from 12 to 144 inches.
| Opening width | Load-bearing header | Allowable span |
|---|---|---|
| 12" to 29" | Double 2x4 | 2'-5" |
| 30" to 43" | Double 2x6 | 3'-7" |
| 44" to 54" | Double 2x8 | 4'-6" |
| 55" to 66" | Double 2x10 | 5'-6" |
| 67" to 77" | Double 2x12 | 6'-5" |
| 78" to 83" | Triple 2x10 | 6'-11" |
| 84" to 96" | Triple 2x12 | 8'-0" |
| 97" to 111" | Quadruple 2x12 | 9'-3" |
| 112" to 144" | Engineered beam required | ā |
For non-load-bearing walls, the calculator returns "Single flat 2x4" for any width up to 96 inches. Above 96 inches it falls back to the same table, because the flat-2x4 allowance only covers openings up to 8 feet.
Openings past what a quadrupled 2x12 spans need an engineered beam, such as laminated veneer lumber (LVL), glulam, or steel, sized by an engineer.
Worked example
| Opening width | Load-bearing? | Result |
|---|---|---|
| 32 in (standard interior door) | No | Single flat 2x4 |
| 36 in (standard exterior door) | Yes | Double 2x6 |
| 60 in (double door) | Yes | Double 2x10 |
| 96 in (8 ft patio door) | Yes | Triple 2x12 |
| 130 in (large opening) | Yes | Engineered beam required |
Example: a 60-inch load-bearing opening. A double 2x4 spans 2'-5" (29 inches), too short. A double 2x6 spans 3'-7" (43 inches), still short. A double 2x8 spans 4'-6" (54 inches), short by 6 inches. A double 2x10 spans 5'-6" (66 inches), which covers 60 inches, so the calculator returns "Double 2x10".
Frequently asked questions
What size header does a 32-inch door need?
In a non-load-bearing wall, a single flat 2x4 is enough for any door up to 8 feet wide, including a 32-inch door. In a load-bearing wall, a 32-inch opening falls in the 30-to-43-inch band, so the calculator returns a double 2x6.
What is the widest opening a doubled 2x8 can span?
Under the load this calculator assumes, 4 feet 6 inches (54 inches). The same member is good for 6 feet 10 inches under the lightest row of the table, where the header carries only roof and ceiling on a 20-foot-wide building with a 30 psf snow load. The span depends on the load, not on the lumber alone.
Does a load-bearing wall always need a doubled header?
Yes. IRC Table R602.7(1) starts at two plies, and the calculator escalates to three and then four plies as the opening gets wider. Openings wider than a quadrupled 2x12 can carry need an engineered beam instead of dimensional lumber.
How do I know if a wall is load-bearing?
A wall is usually load-bearing if it runs perpendicular to the floor or ceiling joists above it, sits directly under a beam or another wall on the floor above, or is an exterior wall. When in doubt, ask a structural engineer or building inspector before cutting into it.
Why does a non-load-bearing door under 8 feet only need a single 2x4?
It carries almost no weight beyond its own and the wall material directly above it. IRC R602.7.3 allows a single flat 2x4 for openings up to 96 inches wide in walls that are not load-bearing.
Does this calculator account for snow load and building width?
Not as inputs. It always uses one tabulated row: roof, ceiling, and one center-bearing floor, a 28-foot-wide building, and 50 pounds per square foot of ground snow. Extra floors above the header, a wider building, or a heavier snow load all call for a larger header than the tool shows.
References
- International Code Council. International Residential Code, Table R602.7(1) "Girder Spans and Header Spans for Exterior Bearing Walls" and section R602.7.3.
- U.S. Department of Commerce. Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (dressed lumber sizes).
- American Wood Council. National Design Specification (NDS) for Wood Construction.