Free under 5 MBSTEP → IGESNo software installation

Convert STEP to IGES online

Convert a STEP or STP (.step, .stp) model to IGES (.iges or .igs) for legacy CAD/CAM systems and suppliers that still require surface-based exchange. Compatible curves and surfaces can transfer, but assemblies, solid-body status, names, colors and product metadata may change.

Encrypted uploads Files up to 300 MB Automatically deleted within 7 days

Upload your STEP file

Choose one STEP file. This page is already configured to create IGES output.

Secure

Drag and drop your STEP CAD file here

or choose a file from your computer

Browse files

Maximum file size: 300 MB

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size.

No STEP file available? Try a STEP sample to see the conversion workflow.

Pricing

Pay as you go, cheaper by the pack

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size. 1 credit downloads any file, any size, and credits never expire.

Starter

3credits

$7.99

$2.66 each

Save 11%

3 downloads of any size. Good for a one-off project.

Pro

5credits

$12.99

$2.60 each

Save 13%

5 downloads of any size. The everyday choice.

★ Most popular

Team

10credits

$19.99

$2.00 each

Save 33%

10 downloads of any size. Best balance of price and volume.

Studio

15credits

$26.99

$1.80 each

Save 40% · best value

15 downloads of any size. Lowest price per file.

Just need one? Pay $2.99 for a single downloadNo subscriptionCredits never expireInvoice on every purchase

No desktop software

Start the STEP-to-IGES workflow in your browser without installing a CAD application or conversion plugin.

Built for legacy compatibility

Move compatible STEP geometry into an IGES workflow while keeping the original STEP file as the source of truth.

Ready to inspect

Open the IGES in the receiving legacy CAD or CAM tool and confirm surfaces, trims, body status, units and assembly structure before production use.

Open IGES viewer

Private file handling

Conversion files stay private, are not added to the public CAD library and are automatically deleted within 7 days.

Continue your workflow

Inspect the STEP, verify the IGES or request specialist help

Inspect the STEP source, verify the translated IGES surfaces and escalate when gaps or lost product structure require specialist repair.

Check the source STEPConfirm that the source STEP opens correctly and contains the expected solids, surfaces and product structure.Open STEP viewerInspect the IGES outputCheck whether the IGES imports as closed bodies, open shells or separate surfaces and whether all trimmed boundaries remain intact.Open IGES viewerNeed healed or rebuilt geometry?Ask a CAD designer to stitch surfaces, repair gaps, rebuild lost features or deliver a native file for the receiving application.Hire a CAD designer

Simple conversion workflow

How to convert STEP to IGES online

Move from a STEP solid or surface model to an IGES surface-exchange file in three steps.

01

Upload the STEP file

Choose a .step or .stp file up to 300 MB. Confirm that it opens correctly before converting.

02

Convert to IGES

The route is preconfigured for IGES output. Start the conversion without searching through a destination-format menu.

03

Download and verify

Open the .iges or .igs result in the target system and compare it with the STEP source for dimensions, surfaces, topology and structure.

Convert STEP to IGES

Format behaviour

What actually happens when STEP is converted to IGES?

STEP can carry B-rep solids, surfaces, assemblies and product information. IGES is commonly used for curves and trimmed-surface exchange. Conversion maps compatible geometry into IGES entities, but receiving applications may import a STEP solid as separate surfaces or an open shell. Assembly hierarchy and richer product metadata may be reduced or omitted.

What is normally retained

  • Compatible curves and surface geometry
  • Overall dimensions and orientation
  • Trimmed surface boundaries where supported
  • Explicit units when translated correctly
  • Separate components or layers only where both the converter and receiving tool support them

What is not retained or may change

  • Native feature history from the authoring CAD system
  • Robust solid-body status when surfaces do not sew after import
  • Assembly hierarchy, constraints and product structure
  • Names, colors, materials and application-specific attributes
  • STEP product metadata without an IGES equivalent
STEP modelSTEP
IGES modelIGES

Format comparison

STEP versus IGES

Choose the format according to what the next application needs—not because one is universally better.

FeatureSTEP STEPIGES IGES
Primary useModern neutral CAD exchange for manufacturing and product structureLegacy curve and surface exchange
GeometryB-rep solids, surfaces and wireframesCurves, wireframes and trimmed surfaces; solid handling varies by importer
StructureCan retain assemblies and product hierarchyOften flatter entity or layer organisation
UnitsSupports explicit unit informationSupports a unit flag, but translation must be checked
MetadataCan carry names, colors and product dataMore limited and inconsistently interpreted across applications

Choose IGES when

A supplier or legacy application specifically requires IGES

Surface and curve exchange is more important than assembly intelligence

The receiving workflow has been tested with .igs or .iges

You will compare the result against the original STEP

Keep STEP when

The receiving application already accepts STEP

You need solid-body reliability or assembly structure

Names, colors or product metadata matter

The model will continue through a modern CAD/CAM workflow

Before continuing

Check the converted IGES before using it

STEP-to-IGES is often a compatibility handoff, not an upgrade. Confirm that the receiving application interprets surfaces and structure correctly.

  1. 01

    Compare dimensions and units

    Measure known features in both files and confirm the same unit system after import.

  2. 02

    Confirm solid or surface status

    Check whether each STEP solid remains closed or arrives as separate surfaces or an open shell.

  3. 03

    Inspect trims and open edges

    Look for gaps, missing patches, duplicated surfaces and broken trim boundaries.

  4. 04

    Review assemblies and components

    Confirm whether hierarchy was retained, flattened or separated into files, layers or entities.

  5. 05

    Check names, colors and layers

    Verify any organisation or visual attributes needed by the receiving team.

  6. 06

    Test the exact legacy application

    Import the IGES into the target CAD/CAM version and run the downstream operation before handoff.

Common problems

STEP-to-IGES troubleshooting

Common issues come from different surface tolerances, limited IGES structure and application-specific import behaviour.

The solid imports as separate surfaces

Cause: The IGES importer did not sew translated surfaces into a closed body.

Fix: Adjust import healing tolerance or stitch the surfaces in CAD.

Gaps appear along trimmed edges

Cause: STEP and IGES represent trims and tolerances differently.

Fix: Run geometry healing and compare the problem area with the source STEP.

The assembly is flattened

Cause: IGES product structure is more limited or inconsistently supported.

Fix: Exchange parts separately or retain STEP when assembly relationships matter.

Names, colors or layers changed

Cause: Attributes did not have a reliable equivalent in the IGES workflow.

Fix: Reapply critical organisation in the receiving tool and keep the STEP source.

The IGES is much larger

Cause: The model was expanded into many individual surface entities.

Fix: Remove unnecessary geometry or exchange only the required components.

The legacy tool rejects the file

Cause: It does not support one or more exported IGES entity types.

Fix: Review its supported IGES entities or ask for a supplier-tested export.

Hire a CAD designer

Secure processing

Your design files remain yours

Engineering files can contain confidential product geometry and documentation. Marathon OS keeps conversion uploads separate from its public CAD library and explains how each file is handled.

Encrypted transfer

Files are transferred over an encrypted connection.

Automatic deletion

Uploaded source files and converted outputs are automatically deleted within 7 days.

You retain ownership

Uploading or converting a file does not transfer ownership of the design to Marathon OS.

Never published automatically

Conversion files are not listed in the public Marathon OS CAD library.

Use tools that support the same STEP-to-IGES workflow.

STEP

Open STEP viewer

Inspect the source geometry

IGES

Open IGES viewer

Check the converted surfaces

IGESSTEP

IGES to STEP

Move legacy surfaces back to modern exchange

STEPSTL

STEP to STL

Create a 3D-printing mesh

STEP3DM

STEP to 3DM

Prepare geometry for Rhino

CAD

Hire a CAD designer

Repair or rebuild failed geometry

Explore a small set of adjacent engineering, mesh and drawing handoffs.

STEPSTL

STEP to STL

CAD to 3D-printing mesh

IGESSTEP

IGES to STEP

Legacy surfaces to modern CAD exchange

STLSTEP

STL to STEP

Mesh to CAD exchange

OBJSTL

OBJ to STL

Mesh handoff for slicing

3DMSTEP

3DM to STEP

Rhino to CAD/CAM exchange

DWGDXF

DWG to DXF

Drawing exchange

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Frequently asked questions

Frequently asked questions about STEP to IGES conversion

Clear answers about output behaviour, compatibility, pricing, file limits and privacy.

  • How do I convert STEP to IGES online?

    Upload the STEP file (.step, .stp), confirm IGES as the preselected output, start the conversion and download the IGES result (.iges, .igs). Verify it in the application used for the next workflow.

  • Why convert STEP to IGES?

    Convert STEP to IGES when an older application, machine workflow or supplier specifically requires .igs or .iges and cannot reliably use STEP.

  • Will a STEP solid remain a solid in IGES?

    Not always. The geometry may import as separate trimmed surfaces or an open shell depending on translation tolerances and the receiving application's IGES importer. Verify body status after conversion.

  • Which STEP and IGES extensions are supported?

    This route accepts .step, .stp input and creates .iges, .igs output.

  • Is the STEP to IGES converter free?

    Files under 5 MB can be converted and downloaded free. Larger files use one credit for one completed download.

  • What is the maximum STEP file size?

    You can upload a STEP file up to 300 MB. Assemblies and complex surfaces can expand into many IGES entities and take longer to import.

  • How are my files handled?

    Files are transferred securely, are not published to the public CAD library and are automatically deleted within 7 days. You retain ownership of the uploaded design.

Need a supplier-tested IGES export?

When the receiving system has strict entity, tolerance or version requirements, work with a CAD specialist who can heal the geometry, validate it in the target application and deliver a production-ready handoff.

Hire a CAD designerConvert another STEP file