IFC Unit Consistency Check

Audit the project's IfcUnitAssignment: verifies unambiguous length, area, volume, and plane-angle units and flags missing or conflicting unit declarations. Run it on its own, or stack it with other checks in the Validation Center.

Audit an IFC model's unit declarations online. Upload the model and find out whether it actually states what its numbers mean — because every length, area, volume and angle in the file is meaningless without the unit assignment that binds them.

Unit problems are the cheapest defect to detect and among the most expensive to discover late. A model whose length unit is missing or contradictory imports at a thousand times the right size, produces quantities out by a factor of a million, or lands a building at a plausible-looking wrong scale that nobody notices until a dimension is checked against a drawing. The file itself carries the answer; this reads it.

When to reach for it: Before a quantity takeoff or federation. Missing or conflicting unit declarations make every downstream area, volume, and length ambiguous — this confirms the project's IfcUnitAssignment is unambiguous first.

What you get: A findings report confirming the declared length, area, volume, and plane-angle units, flagging any missing or conflicting declarations — exportable to BCF, HTML, or CSV.

Example: Confirm the model's units are unambiguous before a quantity takeoff or federating with other disciplines.

What it audits, and how it ranks the findings

An IFC project declares its units once, in an IfcUnitAssignment, and every measured value in the file is interpreted against it. The check audits that declaration directly.

No unit assignment at all — HIGH. Every measure in the model is ambiguous; nothing downstream can interpret a single number with confidence.
Missing length unit — HIGH, and the most consequential single omission, because length underpins geometry, placement and most derived quantities.
Missing area, volume or plane-angle unit — MEDIUM. Quantities and angular values become unreliable, but geometry still places correctly.
Two or more units declared for the same type — MEDIUM. A conflicting assignment means different consumers may resolve the same value differently, which is worse than a missing declaration because it looks complete.

Conceptual findings — nothing to click, and that's correct

Every finding here is conceptual rather than anchored to an element, because a unit declaration has no GlobalId to point at. There is nothing to isolate in the 3D view and no element list to work through; the finding describes the project, and the fix is at project level. That's worth knowing before you go looking for the highlight that other checks give you.

It also means the check is fast and needs no geometry processing — it reads the declaration, not the model. On a large file it finishes while a geometry-based check is still tessellating.

Fixing units properly

Convert IFC Units changes a model's declared units and rescales its geometry to match, which is the real fix when a model is in the wrong unit. Get IFC File Info shows what the file currently declares if you just want to look before deciding.

What NOT to do is apply a scale factor at the receiving end. It works for one import and leaves the model wrong for everyone else — and once two people are applying different compensations to the same file, reconciling quantities becomes archaeology. Run this check on incoming models before they enter a federation or a takeoff, and stack it with the other atomic checks in the Validation Center.

How to check IFC unit declarations

Upload your IFC file
Click Run — no configuration needed
Review the declared length, area, volume, and plane-angle units and any conflicts
Export to BCF, HTML, or CSV

Under the hood

BIMCamel parses IFC files in the browser using the open-source web-ifc engine and renders models with @thatopen/components + three.js. Heavy operations (clean / optimise / validate / convert) run on disposable server-side workers using the same web-ifc stack plus our own .NET pipeline; results stream back to your browser as soon as they're ready. Uploads sit on our servers only as long as your tier's retention window allows and are never used to train AI.

Frequently asked questions

How do I find out what units an IFC file uses?

Run this check, or Get IFC File Info for a plain read-out. The check goes further: it reports missing declarations, conflicting ones, and which of them matter most, rather than only telling you what's there.

Why does my model import at the wrong scale?

Usually because the length unit is missing or contradictory, so the receiving tool assumes one. Both cases are reported here as High findings. Fix it with Convert IFC Units rather than applying a scale factor on import, which leaves the file wrong for everyone else.

Why is a missing length unit worse than a missing area unit?

Because length underpins geometry and placement — without it, nothing in the model can be interpreted at all. A missing area or volume unit makes quantities unreliable but leaves geometry placing correctly, so it's rated Medium rather than High.

Why can't I click through to an element from these findings?

Because a unit declaration has no element to point at — these findings are conceptual and describe the project, not a specific object. The fix is at project level, via Convert IFC Units.

Does this check need to process the geometry?

No — it reads the project's unit declaration, so it finishes quickly even on very large models. That makes it a cheap first check to run on any incoming file.

What's the maximum IFC file size?

Up to 25 MB as a guest, 100 MB with a free account, 500 MB on Pro, and 1 GB on Team. The caps are on upload size only — every tool itself is available on every tier.

What happens to my file after processing?

Your file is uploaded over HTTPS and processed on our servers. Guest uploads are stream-only — the working files are deleted as soon as your download finishes. Free accounts keep results for 7 days; Pro keeps them 90 days and Team 180 days. Files are never shared with third parties or used to train AI.

Is IFC Unit Consistency Check free?

Yes. IFC Unit Consistency Check is free to use — guests get 3 runs a day with 25 MB uploads, and a free account raises that to 10 runs a day with 100 MB uploads. No trial clock, no watermarks.