Free online STP to IGS converter

Convert STEP CAD models to IGES for legacy CAD, CNC, inspection, and CAM software.

Convert STP to IGS online - free

.stp .igs

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How to convert stp to igs file

September 1, 2026
CAD formats
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Legacy CAD, CNC, inspection, and metrology software may accept IGES files but not newer STEP files. Converting the model provides an .igs or .iges file for that application while preserving the original STEP file for future editing and exchange.

What the STP format is

STP files, usually identified by .stp or .step, use the ISO 10303 STEP standard for exchanging 3D product data. They can contain precise solid and surface geometry, assemblies, part names, colors, and other product-structure information.

Mechanical CAD systems such as SolidWorks, Autodesk Inventor, Fusion, CATIA, Siemens NX, and FreeCAD open or create STEP files. STEP is commonly used to receive supplier models, transfer designs between CAD platforms, and import manufacturer-supplied components.

What the IGS format is

IGS files, also commonly named with the .iges extension, use the Initial Graphics Exchange Specification. IGES is an older neutral CAD format that represents wireframes, curves, surfaces, and, in some implementations, solid geometry as IGES entities.

IGES remains useful when a legacy CAD, CAM, CNC, inspection, or engineering application requires it. It generally carries less assembly, feature, parametric, and product-structure information than STEP, and its surface-based data is more likely to need repair after import.

How to convert STP files to IGS

FreeCAD provides a practical desktop method:

Open FreeCAD and choose File → Open.
Select the .stp or .step file and wait for all parts to load.
Check the model tree and 3D view. Select all objects required in the output, or select one body or component when exporting only part of an assembly.
Choose File → Export.
In the file dialog, select an IGES type such as IGES (*.igs *.iges), choose a destination, and save the file.
Open the exported file in the target CAD, CAM, or inspection software and check geometry, units, scale, and assembly placement.

Commercial CAD systems use a similar workflow: open the STEP file, select the required bodies or components, then use File → Save As or File → Export and choose IGES/IGS. Export individual bodies when the receiving application expects separate surface or part files rather than one assembly export.

You can also convert the file for free on 101convert.com without installing software: upload the STP file, choose IGS as the output format, start conversion, and download the result. Avoid uploading confidential designs unless the service's handling and retention terms are acceptable; use desktop CAD software for restricted models.

Quality and compatibility limits

This is a format translation, not an extension change. The conversion writes STEP geometry as IGES entities, so parametric history, feature trees, constraints, materials, assembly relationships, PMI, and some colors may not transfer.

An IGES export may contain trimmed surfaces rather than a watertight solid. Check for missing faces, open gaps, duplicate surfaces, inverted normals, failed joins, and incorrect assembly positions. Confirm that the export and import units match the source model; a millimeter-to-inch mismatch can change the apparent scale without visibly corrupting the shape.

For manufacturing or inspection, verify critical dimensions, tolerances, and fit in the target system before production. Keep the original STEP file as the authoritative source because it normally retains more complete geometry and product-structure data than the converted IGES file.

STP vs IGS: format comparison

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

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

Open STP file Open IGS file

Frequently asked questions

Is the STP to IGS converter free?

Yes, converting STP to IGS 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 STP file be?

You can upload STP 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 STP to IGS?

No. The STP to IGS 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 STP file for this STP to IGS 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.

Will converting STP to IGS remove my CAD model's feature history and parametric edits?

Yes, the result is usually a geometry exchange file rather than an editable feature tree. Solid and surface geometry may remain, but sketches, constraints, timeline features, and other native parametric data are generally not preserved.

Does STP to IGS preserve assemblies, layers, colours, and part names?

Basic geometry usually transfers, but assemblies and model metadata may be simplified or flattened, and colours, layers, names, or attributes can be lost depending on the source and the IGES entities supported. Check the converted model if those details are important.

Why does my IGS file have missing faces or gaps after converting from STP?

IGES represents geometry differently from STEP, so unsupported entities, small edges, or imperfect surface stitching can produce gaps or missing faces. This is more likely when the STEP model contains complex solids, advanced surfaces, or assembly-level data that the IGES representation cannot express cleanly.

Will an STP to IGS conversion change the model's dimensions or units?

It should preserve the model's intended dimensions, but unit interpretation can cause apparent scaling problems if the source unit information is missing or the receiving CAD program interprets the IGES units incorrectly. Verify the units and measure a known feature after conversion.

stp to iges stp to image

Additional formats for
stp file conversion

Reverse conversion

igs to stp

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