Open-Source Steel Takeoff Software: What Exists in 2026
There is no open-source software that reads structural drawings and produces a steel takeoff. Open-source tools exist for steel design and analysis, for CAD, and for section-property lookups. None of them finds W12X26 on a plan sheet, counts it, and rolls it into tonnage. That step is still done by hand, with a PDF viewer and a spreadsheet, or by commercial software.
If you came looking for a free way to avoid paying for estimating software, the practical answer is a mix: free reference data, a free spreadsheet, and a free tier or trial of a steel-specific tool for the part that takes the time. The rest of this page walks through what's actually out there so you don't burn a weekend on a dead end.
What does "open-source steel software" actually cover?
Search for it and you'll find three different kinds of tools. Only the third is anywhere near takeoff.
| Kind of tool | Examples | What it does | Does it do takeoff? |
|---|---|---|---|
| Structural analysis / design | PyNite, OpenSees | Models loads and member forces for an engineer | No |
| CAD / modeling | FreeCAD | Draws geometry, including a BIM workbench | Only if you model the whole building yourself |
| Section data libraries | steelpy (Python, MIT license) | Section properties and AISC shape data in code | Lookups only, no drawing reading |
These are real tools and good at their jobs. They're built for engineers designing a structure, not for estimators pricing one. An estimator receives a finished set of PDFs. The design model usually isn't in the package, so analysis software has nothing to work from.
Why hasn't anyone built an open-source steel takeoff tool?
Because the hard part isn't the weight lookup, it's reading the drawing. A takeoff tool has to:
- Find every member label on every sheet, including labels split across text lines or drawn as strokes.
- Tell a beam callout from a plate note, a detail reference or a bolt count.
- Handle schedules, where the size lives in a table and the plan only shows a mark.
- Avoid counting the same member twice when it appears on a plan, a section and an elevation.
- Cope with scanned sheets, which have no text layer at all.
Each of those takes real engineering and a lot of drawings to test against. Estimating drawings are also mostly confidential, so there's no big public training set for a community project to learn from. That's a large part of why the category is commercial.
What can you build yourself for free?
You can cover about half of the workflow at no cost. The measuring and typing is still on you.
- Free section data. AISC publishes its shapes database as a free download. Our guide to the free AISC shapes database covers where to get it and how to use it for weights. For individual sections, the SteelFlo shapes reference has a page per W, HSS and angle designation.
- A free spreadsheet. Our free Excel takeoff template looks up weight per foot for 4,500+ sections across six standards. No email gate.
- A free PDF viewer. Any viewer that can zoom, search and annotate works. Search for
W12and you'll jump to each hit, but you're still reading every result and deciding whether it's a member. - Free weight formulas. Steel weighs 3.4028 lb/ft per square inch of cross-section. Our steel weight calculation formulas post covers plates, bars, tubes and pipe.
Together that's a working manual process. It's accurate if you're careful, and it's the same method estimators used before software. The cost is time, and it grows with the sheet count. For the error rates that come with it, see manual steel takeoff errors.
Where do free tiers and trials fit in?
For the drawing-reading step, the closest thing to free is a free plan or a trial of commercial software. They're not open-source, but they cost nothing to try on a real job.
- SteelFlo has a free plan: 3 AI takeoffs on your own drawings, unlimited manual estimates, and a CSV export of the bill of materials. No credit card.
- General takeoff tools like Bluebeam, PlanSwift and On-Screen Takeoff offer time-limited trials. They measure and count on any trade's drawings, but you set up the steel sections and weights yourself.
We compare all seven in Free Steel Takeoff Software: 7 Options Compared. Terms change often, so confirm on each vendor's site.
The best test is a job you've already taken off by hand. You have an answer key, and you'll see quickly whether the tool finds what you found.
So which route makes sense?
| Your situation | Best free route |
|---|---|
| A few small jobs a year, under ~10 sheets | Spreadsheet template + AISC data + PDF viewer |
| One or two mid-size jobs, a deadline, no budget | Free plan or trial on a live bid, spreadsheet as backup |
| Regular bidding, sheet counts in the dozens | Evaluate steel-specific software on your own drawings |
| Engineer checking a design | Open-source analysis tools are a fit here |
If you're weighing a paid tool later, what steel takeoff software costs lays out the ranges.
Bottom line
Open-source steel takeoff software doesn't exist yet. Open-source steel design tools do, and they're useful, but they solve a different problem. For takeoff, assemble free data and a template for small jobs, and use a free plan or trial when drawing volume makes manual counting the bottleneck. You can start on the SteelFlo free plan with no card.
Frequently Asked Questions
Is there open-source structural steel takeoff software?
No. Open-source tools exist for structural analysis (PyNite, OpenSees), CAD (FreeCAD) and section data (steelpy), but none reads drawings and counts members into a bill of materials. Takeoff from PDFs is done manually or with commercial software.
What are the best free alternatives to paid steel estimating software?
Three practical options: a free Excel template with weight lookups, AISC's free shapes database for section data, and the free plan or trial of a steel-specific takeoff tool for the drawing-reading step. Each one covers a different piece of the workflow.
Can I use free engineering software for steel takeoff?
Not directly. Analysis tools like PyNite and OpenSees need a structural model as input, and estimators usually receive PDF drawings instead. They're built to check a design, not to count members from sheets.
Is there a free AISC shapes database?
Yes. AISC offers its shapes database as a free Excel download on aisc.org. See our guide to the free AISC shapes database for what's in it and how to use it in a takeoff.
What's the cheapest way to do a steel takeoff?
For small jobs, a free spreadsheet template plus a PDF viewer costs nothing but your time. For larger jobs, the time cost usually outweighs the software cost, so test a free plan on one real bid before deciding.