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Structural · Steel

Historic Steel Beam Identifier

Measured an existing beam and need to know what it is? Enter the dimensions to rank the closest AISC shapes by weighted distance, with a confidence badge and the math shown.

Suspected shape

Narrows the search. Leave on Any if you are not sure.

Top of flange to bottom of flange.

= 1' 1/4" (12.25″)

For HSS, use the overall width.

= 6 1/2" (6.5″)
Sharpen the match (optional)

Weighted ×2 in the score.

Weighted ×2 in the score.

lb/ft

A rolled-in mill mark is the strongest clue — weighted ×3.

Activates with the full 1873–2016 historic dataset — it has no effect on the current seed shapes.

Best match
Exact match
W12X26
Weight
26lb/ft
Depth
12.22in
Score
0.32
Type
W
d12.22"bf 6.49"tw 0.23
Top 5 candidates
  1. 1W12X26score 0.32Exact match
  2. 2W12X30score 0.88Exact match
  3. 3W12X50score 13.12Long shot
  4. 4HSS12X8X3/8score 14Long shot
  5. 5W12X40score 14.52Long shot
ƒShow the distance math
  1. 1.Depth distance
    |measured d − shape d| ÷ 0.125″
    |12.25 − 12.22| ÷ 0.125
    = 0.24
  2. 2.Flange-width distance
    |measured bf − shape bf| ÷ 0.125″
    |6.5 − 6.49| ÷ 0.125
    = 0.08
  3. 3.Total distance scoreper spec §5 weighted distance

    Lower is closer. Exact ≤ 1 · Probable ≤ 3 · Possible ≤ 6.

    = 0.32 → W12X26 (Exact match)
Before you rely on this
  • Historic steel varies in grade (Fy ~24–36 ksi, era-dependent). Identification is for research only — any structural reuse must be verified by a licensed engineer.
  • Match by geometry alone can be ambiguous: rolled-shape dimensions were re-standardized over the years and mill tolerances overlap. Confirm with a stamped weight or mill mark where possible.
  • This build matches against the seed shape subset (current AISC profiles). Era filtering and the full 1873–2016 historic table activate when the v16.0H dataset is generated via build.mjs.

How the identifier works

Rolled steel shapes come in a fixed catalog, so identifying one is a nearest-match problem: find the catalog shape whose dimensions are closest to what you measured. Each candidate gets a weighted distance score, and the smallest wins.

score = |Δd|/0.125 + |Δbf|/0.125 + |Δtf|/0.0625 ×2 + |Δtw|/0.0625 ×2 + |ΔW| ×3

  • Depth and flange width do the coarse sorting — measured in eighths of an inch.
  • Flange and web thickness separate light from heavy beams at the same depth — weighted double.
  • A stamped weight per foot is the strongest single clue and is weighted triple.

This build searches a seed subset of current AISC profiles. The full 1873–2016 historic table and era filtering activate once the AISC v16.0H dataset is generated with the build script.

Frequently asked

How do I identify an existing steel beam?
Measure the overall depth (flange to flange) and the flange width, then, if you can reach them, the flange and web thickness. Enter them here and the tool ranks the closest AISC shapes by a weighted distance score. A stamped mill mark, if legible, is the strongest confirmation — rolled-in weight per foot is weighted heavily in the match.
How does the matching score work?
Each candidate shape gets a distance score: depth and flange-width differences are measured in units of 1/8 inch; measured flange and web thickness in units of 1/16 inch and weighted double; a stamped weight in lb/ft is weighted triple. Lower is closer — the tool calls it an exact match at a score of 1 or less, probable at 3, possible at 6.
Can I reuse an old steel beam structurally?
Only after a licensed engineer verifies it. Dimensional identification tells you the likely shape and section properties, but not the steel's grade or condition. Yield strength of older steel varies with era and mill (roughly Fy 24–36 ksi), and corrosion, prior loading, and notches all matter. Treat this tool as research, not an approval to reuse.
The dimensions do not match any shape exactly — why?
Rolled-shape dimensions were re-standardized several times over the last century, paint and fireproofing add thickness, and mill tolerances overlap between neighboring sizes. If nothing scores as an exact match, look at the top few candidates as a set and confirm with a stamped weight or an engineer's inspection.
What if I can only measure the depth?
You need at least a depth and a flange width to search — depth alone matches too many shapes across different weights. Add flange and web thickness to separate a light beam from a heavy one at the same nominal depth, since those grow with weight while the nominal depth stays roughly constant.

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Sources & references

Identification is for research only. Any structural reuse of existing steel must be verified by a licensed professional engineer — grade, condition, and prior loading cannot be read from dimensions.

Estimates for planning purposes only. Verify all results against the code edition adopted in your jurisdiction and with your Authority Having Jurisdiction (AHJ). This tool is not a substitute for a licensed professional engineer. See our methodology, sources, and code editions.

Data: AISC Shapes Database v16.0, © AISC — used per its developer-use provision.