Convert STP to IFC in your application
3D InterOp is a CAD interoperability SDK that lets your software read STP files and write IFC, writing the exact geometry into a format that can also hold facets.
Spatial does not offer an online converter or a desktop conversion app. 3D InterOp is a component that software vendors embed in their own products.
- Reads STEP · Writes IFC
- Exact geometry → mixed-geometry format
- C++ / C# APIs
STP to IFC at a glance
STEP stores exact geometry; IFC can hold exact solids and facets. What ends up in the IFC file depends on what the IFC writer writes, as detailed below.
| STEP (source) | IFC (target) | |
|---|---|---|
| Full name | Standard for the Exchange of Product model data | Industry Foundation Classes |
| Standard / owner | ISO 10303 — AP203, AP214, AP242 | buildingSMART, ISO 16739 |
| File extensions | .stp, .step | .ifc, .ifczip |
| Geometry | Exact B-Rep | Exact B-Rep and tessellated geometry |
| Assemblies / structure | Yes | Yes: spatial and element hierarchy |
| PMI | Graphical and semantic (AP242) | Not part of the IFC schema |
| 3D InterOp support | Read and write | Read and write |
What's preserved, what changes
Here is what your application can expect to carry across from STEP to IFC.
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Preserved
Exact geometryExact B-Rep read from STP is written to IFC as exact geometry.
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Preserved
Product structureThe STP product structure is written to IFC.
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Improved
Healed geometry3D InterOp repairs and heals STEP data during translation.
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Not carried
PMIIFC has no PMI, so the PMI read from STP isn’t written. Keep STEP AP242 as an output when PMI matters.
Why software vendors add STP to IFC conversion
Open BIM deliverables
Many projects specify IFC deliverables. Writing it lets your users meet those requirements from your software.
Coordination and clash detection
Coordination tools gather models from every discipline in IFC. Your users can contribute without a round trip through another tool.
Facility and asset data
Owners and operators often receive building data as IFC for asset management after handover.
Things to check before you ship
- Written IFC versions: IFC2x3 to IFC4x3 ADD2 (.ifc).
- Exact B-Rep needs IFC4 or later; IFC2x3 files only get tessellation.
- STP has no BIM semantics: check which IFC class your application assigns to each object.
- Supported STP input: AP203, AP214 and AP242.
- Validate a sample of translated files in the target system your users actually work with.
Working with Spatial was a real milestone for us: Thanks to the powerful 3DInterOp library, we were able to successfully bring our complex CAD-based solutions to the cloud while remaining flexible to meet individual customer requirements. For us, Spatial is not just a technology partner, but a true enabler of our product strategy.
Dr. Arno Michelis, Founder, Simus Systems
Read the Case StudyAbout the formats
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Source format
What is a STEP (.stp) file?
STEP is the ISO 10303 standard for exchanging 3D product data between CAD systems. Its application protocols range from exact geometry (AP203, AP214) to full model-based definition with PMI (AP242).
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Target format
What is an IFC (.ifc) file?
IFC is the open, vendor-neutral standard for exchanging building information models, maintained by buildingSMART and published as ISO 16739. It carries building elements with their geometry, properties and relationships.
Frequently asked questions
The exact B-Rep that 3D InterOp reads from STP is written to IFC.
IFC has no PMI, so the PMI read from STP isn’t written. When PMI matters, offer STEP AP242 as an output.
Yes. 3D InterOp reads the STP product structure and writes it to IFC.
Write IFC4 or later to keep exact B-Rep: IFC2x3 files only get tessellation. 3D InterOp writes IFC2x3 to IFC4x3 ADD2.
STP has no BIM semantics, so your application decides which IFC class each object is written as.
3D InterOp reads AP203, AP214 and AP242.
3D InterOp writes IFC2x3 to IFC4x3 ADD2 (.ifc).
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Building software that needs to convert STP to IFC?
3D InterOp is an SDK that lets your application read STEP and write IFC alongside 30+ CAD and BIM formats.