Free online IGS to STP converter

Convert legacy IGES geometry to a compatible STEP file for CAD and manufacturing workflows.

Convert IGS to STP online - free

.igs .stp

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How to convert igs to stp file

September 3, 2026
CAD formats
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A supplier portal, CAD application, CNC workflow, or PLM system may require STEP when it cannot import legacy IGES data. Converting the model creates a neutral file suited to modern CAD exchange without changing the original source file.

What the IGS format is

IGS, also stored as .iges, is the usual filename extension for IGES (Initial Graphics Exchange Specification). It is a vendor-neutral CAD exchange format used for wireframes, curves, surfaces, trimmed surfaces, and, in some exports, solid geometry.

Mechanical, aerospace, tooling, manufacturing, and industrial-design teams use IGES when exchanging data between different CAD systems or opening legacy models. Older versions of applications such as CATIA, AutoCAD, Solid Edge, SolidWorks, Creo, and Rhino commonly support it.

IGES normally transfers geometry rather than native design intelligence. Feature history, parametric constraints, native sketches, assembly relationships, and material metadata may be absent. Many IGES files import as separate surfaces instead of a single watertight solid.

What the STP format is

STP, also stored as .step, is the common filename extension for STEP, the ISO 10303 family of product-data exchange standards. STEP is widely supported by mechanical CAD, manufacturing, inspection, and product-lifecycle-management software.

STEP commonly stores precise boundary-representation geometry and can carry more product, assembly, and manufacturing information than a basic IGES exchange. AP203 and AP214 are established mechanical-CAD application protocols; AP242 is a newer option for product and model-based engineering data. Support depends on the receiving application.

Changing .igs to .stp does not perform a conversion. The IGES geometry must be imported, checked or repaired when necessary, and written with a STEP exporter. STEP also does not normally recreate the original feature tree or parametric history.

How to convert IGS to STP

Using FreeCAD

Keep an untouched backup of the original model.igs or model.iges file.
Open FreeCAD and select File → Open, then choose the IGES file.
Inspect the imported geometry in the 3D view. Look for missing faces, open edges, separated surfaces, incorrect components, and wrong scale.
Switch to the Part workbench. Select the imported shape and run Part → Check geometry when available to detect invalid topology.
Repair or sew surfaces if the destination requires a solid. Hide construction geometry and select every body or component that should be exported.
Use File → Export, choose a STEP output type, and save the result as model.stp or model.step. The extension is interchangeable; the exported STEP content is what matters.
Reopen the exported file in FreeCAD or the destination CAD system. Check body count, assembly components, units, overall dimensions, and critical faces.

For a conversion without installing desktop software, the built-in converter at 101convert.com can process an IGS file and produce STP for free. Upload the source, select STP or STEP, run the conversion, and download the result; do not submit confidential engineering data unless the organization permits online processing.

Using other CAD software

Commercial CAD systems generally use the same sequence: import the IGES file, inspect or repair the resulting surfaces, then use File → Save As or File → Export and select STEP. In SolidWorks, for example, open the IGES file, review the imported-body options, and save it in a STEP format. Other systems may expose STEP schema, unit, sewing, or assembly-export settings in an import or export dialog.

Quality and compatibility limits

Surface imports may not be solids. Gaps, mismatched edges, sliver faces, and bad trimming can prevent sewing or solid operations. Repair the model before export when the receiving system needs a closed volume.
Missing CAD intelligence cannot be restored. A conversion cannot recreate feature trees, sketches, constraints, or native parametric history that the IGES file did not contain.
Verify units and scale. Both formats can store units, but legacy files or importer settings can cause millimeter-to-inch errors. Measure a known dimension after import and after export.
Confirm the export scope. Depending on the software, export may include only selected or visible objects rather than the whole document. Check hidden bodies, assemblies, and components explicitly.
Compare critical geometry. Tolerance differences and repair operations can affect small holes, fillets, thin walls, and mating faces. Measure these features before manufacturing or inspection.
Use a compatible STEP protocol. AP242 may preserve more product information, but an older recipient may support only AP203 or AP214. Select the schema required by the receiving system rather than assuming the newest protocol will work.

IGS vs STP: format comparison

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

Comparison of the IGS and STP file formats
Property	.IGS Initial Graphics Exchange Specification	.STP STEP (Standard for the Exchange of Product model data)
Dimensions	3D	3D
Geometry	Both	Both
Layers	No	—
Materials	Limited	Limited
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

Open IGS file Open STP file

Frequently asked questions

Is the IGS to STP converter free?

Yes, converting IGS to STP 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 STP?

No. The IGS to STP 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 STP 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 IGS to STP preserve my CAD geometry?

Usually, the main curves, surfaces, and solid geometry are transferred, but the result depends on which IGES entities the converter can map to STEP. Small gaps, missing surfaces, or altered trims can appear when the source geometry is incomplete or difficult to translate.

Will my IGS feature history and sketches stay editable in STP?

No, IGES files generally do not contain the native parametric feature history, constraints, or design-tree structure needed to preserve that editability. The STEP result is typically editable as imported CAD geometry, but not as the original model with its design features.

Why does my STP file show gaps or surfaces instead of a solid?

This usually happens because the IGS file contains unstitched surfaces, open boundaries, or unsupported geometry rather than a complete watertight solid. STEP can preserve those surfaces, but it cannot reliably create a valid solid when the source topology has missing or mismatched edges.

Will units, colors, layers, and assembly information convert from IGS to STP?

Basic units and some display or organization information may transfer, but colors, layers, part names, and assembly structure are not guaranteed to map exactly between IGES and STEP. Check the resulting model because legacy IGES files often store less product-structure information than a modern STEP file.

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