Beam Span Calculator
Built-up girder and beam spans read straight off IRC 2021 Table R602.7(2) for interior bearing walls and Table R602.7(1) for exterior walls, with the required jack studs returned alongside the span. Two, three and four ply members from 2x4 to 2x12, indexed on building width and on what the beam is carrying.
This is the check you run before quoting a load-bearing wall removal, when you need to know whether the opening is a table lookup or a stamped design.
Same beam, three answers, and the building decides
- Triple 2x10, interior bearing wall, carrying one floor
- 12 ft building width: 11 ft 5 in
- 24 ft building width: 8 ft 1 in
- 36 ft building width: 6 ft 7 in
Nearly five feet of difference on the same three pieces of lumber. This is why a remembered span never survives the next house.
Four things that decide the beam
Tributary width beam sizing, done by the table
A girder carries half the joist span on each side, so a beam sitting between two 12 ft joist spans carries 12 ft of building width. IRC 2021 Tables R602.7(1) and R602.7(2) index directly on building width for exactly that reason, which means you match your tributary width to the table column rather than computing a load in pounds. The tabulated buckets are 12, 24 and 36 ft, and the tool rounds up to the next one rather than interpolating between them.
What the beam is carrying
Roof and ceiling only, one floor, or two floors changes the answer more than adding a ply does. On a 24 ft building width, a triple 2x10 interior girder spans 8 ft 1 in under one floor and 5 ft 6 in under two. A triple 2x12 in the same wall goes 9 ft 6 in under one floor and 6 ft 5 in under two. Counting the floors above the wall correctly is the single most common error on a wall removal quote. A roof-and-ceiling-only wall sits higher again.
Plies and depth
Depth buys more than plies do. On a 24 ft width carrying one floor, a double 2x10 reads 6 ft 6 in and a triple 2x10 reads 8 ft 1 in, while a triple 2x12 reads 9 ft 6 in and a four-ply 2x12 reaches 11 ft 0 in. The triple 2x10 beam span is the figure most framers carry in their head, and it is also the one that moves the most between houses. A built-up girder span table only works if the plies act together, so the nailing pattern that fastens them is part of the design, not a detail.
Jack studs, returned with the span
How many jack studs for a header is not a separate calculation. The IRC header and girder tables print the required jack studs in the table itself, keyed to the member and the span, and this tool returns that number with every result. King studs run full height beside them, and the bearing length at each end still has to carry the reaction down a continuous load path. Two jacks on one member and one on the next is normal rather than an error.
Beam span for load bearing wall removal is where the table usually stops
Removing a bearing wall concentrates load onto new posts and demands a continuous load path all the way down to a footing, which the IRC prescriptive tables do not address. That is a licensed structural engineer's scope in every jurisdiction we could find, and most building departments require stamped drawings for the permit. The table also stops applying when a point load lands on the beam from a post, a girder end or a ridge beam reaction, when ground snow load falls outside the tabulated range, when the member is steel, LVL, LSL, PSL or glulam rather than sawn dimension lumber, or when the building official asks for calculations. Engineered lumber is never in these tables: those spans come from the manufacturer with matching load assumptions, or from an engineer.
One dataset, three IRC tables, checked against the printed text
Most beam span calculators on the web will not tell you which code edition they run, which table the number came from, or whether the transcription was ever verified. Here is ours in full.
Three tables, not one
The dataset carries IRC 2021 Table R602.7(1) for exterior bearing walls, Table R602.7(2) for interior bearing walls, and Table R602.7(3) for open porch headers, plus the jack stud count that each table prints beside the member.
Verified against the code text
Values were taken from the 2021 Seattle Residential Code Chapter 6 PDF, pages 6-15 to 6-17, which reproduces these IRC tables verbatim with no local amendments in them, and were checked against that printed text rather than retyped from a summary.
Grade, stated plainly
The IRC prints a single combined value for Douglas Fir-Larch, Hem-Fir, Southern Pine and SPF at No.2, so species does not move the answer here the way it does on a floor joist. No.2 is the only grade these tables carry.
6’-6″
Interior bearing wall, one floor above, 24 ft building width. Two jack studs each end.
8’-1″
Adding the third ply buys 19 inches, which is often the difference on a kitchen opening.
9’-6″
Going up in depth instead buys more than the ply did. Depth is the cheaper move.
11’-0″
The deepest built-up member the table carries. Past this it is engineered or stamped.
All four are No.2 sawn lumber on an interior bearing wall carrying one floor at a 24 ft building width. Put a second floor on the same wall and the triple 2x10 drops from 8 ft 1 in to 5 ft 6 in. Building width and the floors above are the two columns people skip.
Code edition, and who actually decides
This tool runs the 2021 IRC tables. The edition your building department has adopted may be older, and states and municipalities amend the model text, so a locally amended table beats anything on this page. IRC R104 and R106 give the building official the authority, and the AHJ is the final word on your permit. A prescriptive girder table is a worst-case lookup, not an engineering calculation, and nothing here is a stamped design.
Sources
- ICC Digital Codes — 2021 International Residential Code, Chapter 6, Wall Construction, for Tables R602.7(1), R602.7(2) and R602.7(3) and section R602.7.
- 2021 Seattle Residential Code, Chapter 6 (PDF), pages 6-15 to 6-17, which reproduces these IRC tables verbatim and was the text the dataset was verified against.
Data retrieved 4 September 2026. Deliberately absent: no steel, LVL, LSL, PSL or glulam spans, because the IRC does not tabulate engineered members; no interpolation between the 12, 24 and 36 ft building width columns, because the tool rounds up to the next tabulated bucket instead; no point-load or cantilever cases, because those leave the prescriptive tables entirely.
Beam and girder span FAQs
How do I figure tributary width for a girder carrying joists from both sides?
Half the joist span on each side, added together. A girder between two 12 ft joist spans carries 12 ft of building width. IRC 2021 Tables R602.7(1) and R602.7(2) index directly on building width for that reason, so you match tributary width to the table column rather than computing a load in pounds. Round up to the next tabulated width.
What is the maximum span for a triple 2x10 built-up girder?
It depends on building width and what sits above, so there is no single number. On an interior bearing wall carrying one floor, a triple 2x10 spans 11 ft 5 in at a 12 ft building width, 8 ft 1 in at 24 ft and 6 ft 7 in at 36 ft. Put a second floor on that wall and the 24 ft figure falls to 5 ft 6 in.
Can I remove this load-bearing wall and put a beam in?
Not off a table. Removing a bearing wall concentrates loads onto new posts and requires a continuous load path down to footings, which the IRC prescriptive tables do not address. That is a licensed structural engineer's scope in every jurisdiction we could find, and most AHJs require stamped drawings for the permit.
How many jack studs does the beam need at each end?
The IRC header and girder tables give the required jack studs in the table itself, keyed to member size and span, so it is not a separate calculation. This tool returns that count with the span. King studs run full height beside the jacks, and the bearing length at each end must carry the reaction. If the table count looks light for your load, it is an engineered condition.
When do I need steel instead of built-up dimensional lumber?
When the span or the load falls outside the IRC tables. The IRC tabulates sawn-lumber girders and headers only; steel, LVL and PSL are not in the tables and require a stamped design or a manufacturer's span chart with matching load assumptions. The moment a point load or an unusual span appears, it goes to an engineer.
Does the interior bearing wall girder span change if the floor above is centre-bearing?
Yes, on exterior walls it does, and the table has separate columns for it. Table R602.7(1) distinguishes clear-span floors from centre-bearing floors, because a centre-bearing floor delivers less load to the outside wall. Table R602.7(2) for interior bearing walls indexes on the number of floors instead, which is what this tool asks for.
Sizing the beam is free. Winning the job is the hard part
Which is why it matters that the homeowners asking you to price a wall removal are the ones who can actually fund the engineering, the permit and the work behind it. Filtering for that before the site visit is a marketing problem, not a framing one.
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Zayn founded Zainfy in 2023 and has spent six years in performance marketing for home remodeling and construction companies across the United States. He built this tool set because the contractors he works with were losing more money to pricing math than to any advertising decision.
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