Convert IFC Units

Convert the project length unit (mm, cm, m, ft, in) and rescale all geometry consistently.

Change an IFC model's length unit and rescale its geometry to match. Upload the model, pick the target unit — millimetres, centimetres, metres, feet or inches — and download a file that declares the new unit and whose coordinates agree with it.

The hard part of a unit change isn't the declaration, it's the consistency. Rewriting the header to say metres while leaving millimetre coordinates in place produces a model that's a thousand times too big and technically valid — the worst kind of broken, because everything opens it happily. Both halves have to move together, which is why this is a tool rather than a text edit.

When to reach for it: When merging models authored in different unit conventions, or a receiving tool expects a specific project unit.

What you get: The model with its unit declaration rewritten and every length value rescaled consistently. Areas, volumes and angles keep their own units.

Example: Convert a millimetre model to metres (or feet) before merging with files from another authoring convention.

Declaration and geometry, together

The project's unit assignment is updated and the geometry is rescaled in the same pass, so the file remains internally consistent. Everything else survives: elements, properties, relationships, GlobalIds and the spatial hierarchy are untouched, so no data workflow is affected by the change.

The run reports the conversion it performed — from-unit to to-unit — rather than just succeeding, and if it can't proceed it says why instead of silently doing nothing. A unit conversion that reports success and changes nothing is a very expensive kind of quiet failure.

Dry run first

Rescaling geometry is the most consequential edit in this toolbox — get it wrong and every dimension in the model is off by a factor. Dry run reports what the conversion would do, including the units it read and the units it would write, and commits nothing. It costs one run to be sure, which is cheap next to discovering the mistake after the model has been issued.

Check what the model currently declares before you start. Get IFC File Info reads the unit assignment directly, and the IFC Unit Consistency Check goes further — it reports missing declarations, conflicting ones, and which of them matter, which is worth knowing because a model with NO length unit needs a different conversation than one with the wrong one.

When to convert, and when not to

Convert when the model's unit is genuinely wrong, when a receiving tool or standard requires a specific unit, or when a project has settled on one convention and an incoming model doesn't follow it. Millimetres are the usual authoring convention for buildings; metres are common for site and infrastructure work; feet and inches appear throughout North American practice.

Don't convert to work around a scale problem at the receiving end. If a model imports at the wrong size, find out WHY first — it may be an export that wrote inconsistent units, in which case the fix is here, or it may be an import setting in the receiving tool, in which case converting the model makes it wrong for everybody else. And don't convert a model whose coordinates are far from the origin expecting the position to improve: that's a different problem, addressed by Transform IFC Model or the Georeference Editor.

How to convert IFC units

Upload your IFC file
Pick the target length unit (mm, cm, m, ft, in)
Click Run to convert
Download the converted IFC

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 change an IFC model from millimetres to metres?

Upload it, choose metres as the target, and run. The project's unit declaration and the geometry are both updated in one pass, so the file stays internally consistent — which is the whole point, since changing only the declaration makes the model a thousand times too big while still being valid IFC.

Which units can I convert between?

Millimetres, centimetres, metres, feet and inches, in any direction. Millimetres are the usual building-authoring convention, metres are common for site and infrastructure, and feet and inches appear throughout North American practice.

Can I preview the conversion first?

Yes — dry run reports the units it read, the units it would write, and what the conversion would do, without committing anything. Worth doing every time: rescaling geometry is the most consequential edit here, and one run is cheap next to finding the mistake after issuing the model.

Will it break my properties or element IDs?

No. Only the unit declaration and the geometry change. Elements, properties, relationships, GlobalIds and the spatial hierarchy are untouched, so no data workflow is affected.

My model imports at the wrong scale — is this the fix?

Sometimes. Find out why first: if the export wrote inconsistent units, this is the fix. If it's an import setting in the receiving tool, converting the model makes it wrong for everyone else. The IFC Unit Consistency Check will tell you whether the model's declarations are actually the problem.

Which IFC versions are supported?

IFC2x3 and IFC4 — the two schema versions exported by essentially every AEC authoring application. IFC4x3, the infrastructure schema, works too: it opens in the viewer, and validation, health reports, property-set editing and georeferencing all run on it. Tools that need geometry processing, such as clash detection and 3D export, aren't verified on IFC4x3 yet.

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 Convert IFC Units free?

Yes. Convert IFC Units 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.