Free online IGS to STEP converter

Convert legacy IGES geometry to STEP for modern CAD and manufacturing workflows.

Convert IGS to STEP online - free

.igs .step

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Max 25 MB per file · No registration required · max 75 MB total

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How to convert igs to step file

August 19, 2026
CAD formats
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A receiving CAD system may require STEP when an older design is supplied as an IGS file, particularly for solid editing, assembly exchange, or manufacturing. Conversion also provides a more compatible handoff to systems with limited IGES support.

What the IGS format is

IGS is the common file extension for IGES, the Initial Graphics Exchange Specification. Files normally use .igs or .iges and store CAD geometry as ASCII text. An IGES file can contain wireframes, curves, trimmed surfaces, and some solid boundary-representation entities, but it usually does not preserve the source model’s feature tree, sketches, constraints, parametric history, or application-specific settings.

CAD systems including CATIA, SOLIDWORKS, Siemens NX, AutoCAD, Rhino, Fusion, and FreeCAD can import or export IGES. The format remains common in legacy engineering archives, supplier exchanges, tooling, and CNC-related workflows.

What the STEP format is

STEP is the ISO 10303 product-data exchange standard, commonly stored with .step or .stp. Mechanical CAD, CAM, inspection, and manufacturing software widely uses it to exchange three-dimensional solid and surface models.

Compared with a typical IGES transfer, STEP more reliably represents boundary-representation solids and can carry assemblies, component relationships, names, colors, and other product data when the exporting and importing applications support those entities. AP203, AP214, and AP242 are STEP application protocols; AP214 and AP242 are common for mechanical CAD, while AP242 is newer and can include additional product-manufacturing information. The receiving system’s requirements should determine which protocol is selected.

How to convert IGS to STEP

Using FreeCAD

Install and open FreeCAD.
Choose File → Open and select the .igs or .iges file. FreeCAD imports the geometry into the document tree.
Inspect the imported model in the 3D view and select the objects to convert. Select all required objects if the file contains multiple parts or surfaces.
Choose File → Export.
In the save dialog, choose a STEP file type if available, or enter a filename ending in .step or .stp. Save the export.
Reopen the STEP file in FreeCAD or the destination CAD system. Check the number of solids, surface continuity, dimensions, orientation, and assembly placement.

FreeCAD is useful for local conversion because it can import IGES and export STEP without the original authoring application. For repeated conversions, FreeCAD can also be automated with Python, but import and export behavior varies by FreeCAD version and by the Open CASCADE libraries installed with it; test automation with representative files.

Using the built-in converter

You can convert the file for free on 101convert.com without installing software. Upload the IGS file, select STEP as the output format, start the conversion, and download the resulting file. Do not upload confidential engineering data unless the applicable security policy permits processing it through a web service.

Quality and compatibility limits

Conversion changes the exchange representation; it does not recreate parametric features or design history that were not present in the IGES file. The resulting STEP model may therefore open as imported or “dumb” geometry rather than as editable sketches and feature operations.

Many IGES exports describe a supposed solid as separate trimmed surfaces. Gaps, incorrect surface orientation, self-intersections, and tolerance differences can stop the importer from creating a valid solid. Run the source or conversion software’s geometry-check and repair tools before exporting, then verify that the STEP file contains the expected number of solids and has no unintended open edges.

Measure a known dimension before and after conversion. IGES unit declarations can be interpreted incorrectly by some software, while STEP normally records units explicitly, but an incorrect import setting can still produce a scale error. Confirm the unit system, coordinate orientation, and model scale in the receiving application.

STEP cannot restore colors, layers, assemblies, metadata, or manufacturing information that the source IGES file did not contain. Even when the IGES file includes such data, preservation depends on the entities supported by the selected STEP application protocol and by both CAD programs.

IGS vs STEP: format comparison

How the IGS and STEP formats compare on the properties that matter most for this conversion.

Comparison of the IGS and STEP file formats
Property	.IGS Initial Graphics Exchange Specification	.STEP Standard for the Exchange of Product model data
Dimensions	3D	3D
Geometry	Both	Both
Layers	No	—
Materials	Limited	Yes
Plain-text readable	No	Yes
Operating system support	Wide	Wide
Typical file size	Medium	Medium
Open standard	Partly open	Yes
Introduced	—	1994
Developer	IGES/PDES organization (later managed by various standards bodies, including ANSI/ASME)	ISO
MIME type	—	application/step

Open IGS file Open STEP file

Frequently asked questions

Is the IGS to STEP converter free?

Yes, converting IGS to STEP on 101convert.com is completely free. No registration, email address or installation is required. If you need a higher file size limit or want to convert more files at once, see our plans.

How large can my IGS file be?

You can upload IGS files up to 500 MB and convert up to 5 files at once in a single batch.

What happens to my uploaded files?

Files are processed automatically and deleted from our servers within a few minutes after conversion. We never view or share your files.

Do I need to install any software to convert IGS to STEP?

No. The IGS to STEP conversion runs entirely online in your browser and works on Windows, Mac, Linux, Android and iPhone.

Did the conversion fail?

In most cases, the cause is an incorrect file format. Please upload a valid IGS file for this IGS to STEP conversion. Occasionally, the issue may be on our side. We analyze recurring conversion failures and disable or fix the converter if we detect a defect.

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Additional formats for
igs file conversion

Reverse conversion

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