Free under 5 MBIGES → STEPNo software installation

Convert IGES to STEP online

Convert an IGES (.iges or .igs) model to STEP (.step or .stp) for modern mechanical CAD, supplier exchange and manufacturing workflows. Compatible curves and trimmed surfaces can transfer, but conversion cannot restore the original feature tree or automatically repair every gap in legacy geometry.

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

Upload your IGES file

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

Secure

Drag and drop your IGES 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 IGES file available? Try a IGES sample to see the 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 IGES-to-STEP workflow in your browser without installing a CAD application or plugin.

Modernize legacy CAD exchange

Move usable IGES geometry into a STEP container that is more common in current mechanical CAD workflows, then verify whether surfaces sew into valid bodies.

Ready to inspect

Open the STEP result in the receiving CAD system and check units, missing entities, open edges, body status and product structure.

Open STEP viewer

Private file handling

Files stay private, are never added to the public CAD library and are automatically deleted within 7 days.

Continue your CAD workflow

Inspect the IGES, verify the STEP or request specialist help

Inspect the IGES source, validate the STEP result and request geometry repair when legacy surfaces do not sew cleanly.

Check the source IGESCheck scale, missing faces, surface boundaries and disconnected geometry before conversion.Open IGES viewerInspect the STEP outputConfirm expected bodies and surfaces, then inspect open edges, units and assembly or naming information.Open STEP viewerNeed repaired solids or native features?Ask a CAD designer to heal gaps, rebuild missing surfaces or recreate editable features in the target CAD system.Hire a CAD designer

Simple conversion workflow

How to convert IGES to STEP online

Move from a legacy IGES model to a STEP exchange file in three steps.

01

Upload the IGES file

Choose a .iges or .igs file up to 300 MB. Confirm that the source opens and contains the expected entities before converting.

02

Convert to STEP

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

03

Download and verify

Open the .step or .stp result in the receiving CAD system. Verify dimensions, surface continuity, body status and completeness.

Convert IGES to STEP

Format behaviour

What actually happens when IGES is converted to STEP?

IGES commonly stores curves, wireframes and trimmed surfaces, often as loosely connected entities. STEP stores B-rep geometry and product structure. Conversion maps compatible entities and may sew adjacent surfaces into shells or solids when tolerances permit. It does not invent missing faces, recover native features or guarantee that an open IGES becomes a solid.

What is normally retained

  • Compatible curves and trimmed surfaces
  • Overall model shape and orientation
  • Explicit unit information where present
  • Entity names or layers when mapping exists
  • Closed shells or solids when surfaces sew successfully

What is not retained or may change

  • Original sketches, constraints and feature history
  • Unsupported or application-specific IGES entities
  • Some layers, colors and metadata
  • Assembly relationships not represented by the source
  • Gaps or invalid trims that require manual healing
IGES modelIGES
STEP modelSTEP

Format comparison

IGES versus STEP

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

FeatureIGES IGESSTEP STEP
Data modelCurves, wireframes and trimmed surfacesB-rep solids/surfaces and product structure
ConnectivityMay contain loosely associated surface entitiesSupports connected topology and solid bodies
AssembliesLimited and inconsistently usedCan represent product/assembly structure
EditabilitySurface and curve editing; no universal feature historyImported geometry; no recovered native feature tree
Best useLegacy CAD/CAM and surface exchangeModern mechanical CAD and supplier exchange

Choose STEP when

A current CAD/CAM system or supplier prefers STEP

You need connected topology or product structure where available

You want a more common mechanical CAD exchange container

You can validate and heal legacy surfaces if required

Keep IGES when

The recipient specifically requires IGES

A legacy system depends on particular IGES entities

You are still repairing the source surfaces

The conversion provides no practical downstream benefit

Before continuing

Check the converted STEP before using it

IGES files often contain tolerance and connectivity problems. A STEP download should be inspected as geometry, not accepted merely because it opens.

  1. 01

    Verify units and dimensions

    Compare a known measurement in the IGES source and STEP result.

  2. 02

    Count expected entities and bodies

    Confirm that no surfaces, curves or components disappeared.

  3. 03

    Inspect open edges and gaps

    Check whether trimmed surfaces sewed into closed shells or remained open.

  4. 04

    Review body status

    Identify solids, shells, compounds and separate surfaces in the receiving system.

  5. 05

    Check orientation and trims

    Look for reversed faces, failed boundaries and sliver geometry.

  6. 06

    Validate product structure

    Confirm names, parts and assembly hierarchy only when the source contained usable structure.

Common problems

IGES-to-STEP troubleshooting

Most problems come from legacy entity support, loose surface tolerances, invalid trims, missing unit context or expecting conversion to heal incomplete geometry automatically.

The STEP remains a surface model

Cause: The IGES surfaces are open or do not meet within sewing tolerance.

Fix: Heal gaps and trims in a CAD system, then convert or save again.

Some faces or curves are missing

Cause: The source contains invalid or unsupported IGES entities.

Fix: Identify the missing entities in the source and re-export using widely supported types.

The model is the wrong size

Cause: Units were absent or interpreted differently.

Fix: Measure a known feature and set the intended unit in the receiving system.

Faces are reversed

Cause: Surface orientation or trim loops were inconsistent.

Fix: Repair face orientation and boundaries in the source or target CAD system.

Assembly structure is missing

Cause: IGES often lacks reliable modern product hierarchy.

Fix: Recreate the required structure after import or use a better source file.

The file opens but cannot be edited parametrically

Cause: STEP contains imported geometry, not the original feature tree.

Fix: Use direct editing or commission a target-native rebuild.

Hire a CAD designer

Secure processing

Your design files remain yours

Engineering files can contain confidential 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 IGES-to-STEP workflow.

IGES

IGES file viewer

inspect the legacy source

STEP

STEP file viewer

verify the converted result

STEPIGES

STEP to IGES

create an IGES handoff

IGESSTL

IGES to STL

create a printable mesh

3DMSTEP

3DM to STEP

convert Rhino geometry to STEP

CAD

Hire a CAD designer

heal or rebuild geometry

Explore adjacent engineering and mesh handoffs.

STEPSTL

STEP to STL

CAD to printable mesh

STLSTEP

STL to STEP

mesh to CAD exchange

OBJSTEP

OBJ to STEP

mesh to CAD exchange

STEPIGES

STEP to IGES

legacy surface exchange

3DMSTEP

3DM to STEP

Rhino to CAD/CAM exchange

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Frequently asked questions

Frequently asked questions about IGES to STEP conversion

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

  • How do I convert IGES to STEP online?

    Upload IGES (.iges, .igs), confirm STEP as the preselected output, convert and download STEP (.step, .stp). Verify the result in the target application.

  • Why convert IGES to STEP?

    Convert IGES to STEP when the receiving CAD/CAM system or supplier prefers STEP and you need a modern B-rep exchange container for legacy surface geometry.

  • Will IGES to STEP turn every surface model into a solid?

    No. Surfaces can form a solid only when they are complete, correctly trimmed and close enough to sew. Gaps or missing faces require repair.

  • Which IGES and STEP extensions are supported?

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

  • Is the IGES to STEP 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 IGES file size?

    You can upload a IGES file up to 300 MB. Legacy files with many surface patches, curves or invalid entities can take longer to process and review.

  • 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.

Need a healed solid or editable feature model?

Conversion can modernize the exchange format, but it cannot invent missing geometry or recover design history. Use a CAD designer when the result needs healing, remodeling, tolerances or target-native features.

Hire a CAD designerConvert another IGES file