What the IGES keeps
- Exact curves and surfaces
- Dimensions in millimetres, with the unit stored
- Every part in its assembled position
- Closed solids as IGES B-rep solids, when they pass our read-back check
Convert STEP or STP to IGES online
Upload a .step or .stp file and download an IGES file with the exact geometry in millimetres, for CAM software, suppliers and older CAD systems. First 2 files free, any size up to 300 MB. After that, 1 credit per file.
STEP to IGES converter
Exact · millimetresSTEP
From STEP.step or .stp
IGES
exact · millimetres
Sign in with Google or an emailed code to upload your own file. The sample file works without signing in.
Drop your STEP file here
or browse files
.step or .stp · up to 300 MBFirst 2 conversions free — any size up to 300 MB. Then $2.99 or 1 credit per file, charged at download. Prices include tax.
Have an IGES file? You can also convert IGES back to STEP.
- Files up to 300 MB
- Exact geometry, no triangles
- Units in millimetres
STEP to IGES converter at a glance
- Converts
- STEP and STP (AP203, AP214, AP242) to IGES (.igs).
- You get
- One IGES file with exact curves and surfaces in millimetres. Closed solids can come out as IGES B-rep solids; if they don't pass our read-back check, you get trimmed surfaces.
- File size
- Up to 300 MB. We email you when the file is ready.
- Price
- First 2 files free, any size up to 300 MB. After that, 1 credit per file.
How to convert STEP to IGES
STEP to IGES in four steps
To convert STEP or STP to IGES, sign in, upload your .step or .stp file above and download the IGES file. The geometry stays exact, with no triangles. Closed solids can be written in IGES B-rep mode, which CAD programs that read it open as solids; otherwise you get trimmed surfaces. STP to IGS works the same way.
Upload
Sign in, then drop a .step or .stp file up to 300 MB onto the converter.
Convert
The exact geometry is written to IGES in millimetres.
Download
We email you when the IGES is ready. Download one IGES file.
Check
Open it in the receiving program and confirm it arrived as solids, not loose surfaces.
STEP vs IGES
What changes when STEP becomes IGES
Both formats store exact geometry. IGES is older and carries less around it.
What it leaves behind
- Part names and the assembly tree
- Colours
- PMI and product metadata
- Feature history, sketches and constraints
Solids or surfaces
How your IGES arrives
IGES can carry solids or loose surfaces. Here's which one you get.
IGESSolids (B-rep mode)
Closed solids can be written as IGES type 186 solids, after a read-back check that the solids survive. Programs that read B-rep IGES open them as solids.
IGESTrimmed surfaces
If the STEP holds surfaces, or the read-back would lose a face or solid, you get type 144 trimmed surfaces. Knit or sew them into a solid in your CAD program.
STEPPrefer STEP when you can
Our IGES doesn't carry names, colours or the assembly tree. STEP does. If the receiver accepts STEP, send the STEP.
Both paths write millimetres and keep the geometry exact. We don't sew or heal faces before writing, so the IGES has the same faces as your STEP. Open the file in the receiving program to see whether it arrived as solids or surfaces.
Choose the right format
STEP vs IGES
Pick by what the next program needs.
| STEP | IGES | |
|---|---|---|
| Standard | ISO 10303, still developed | IGES 5.3, last updated in 1996 |
| Geometry | Exact solids and surfaces | Exact curves and surfaces; solids in B-rep mode |
| Units | Stored | Stored (ours is mm) |
| Names, colours and assembly tree | Yes | Not in ours |
| Best for | Modern CAD exchange | CAM, older CAD and suppliers who ask for it |
IGESConvert to IGES when
STEPKeep STEP whenA supplier, CAM program or older CAD system asks for IGES or IGS.
You're in the right placeThe receiver accepts STEP: it carries names, colours and the assembly.
Open the STEP viewer BREPChoose BREP whenThe model is going into FreeCAD, CadQuery, gmsh or other Open CASCADE tools.
STEP to BREP for OCCT toolsOpen it anywhere
Where IGES files open
Most CAD and CAM programs import IGES.
SolidWorksImports IGES
FusionImports IGES
RhinoImports IGES
MastercamImports IGES
CATIAImports IGES
FreeCADImports IGES
If a program asks how to import IGES, choose the option that keeps solids or knits surfaces into solids.
FAQ
STEP to IGES questions
Solids or surfaces, units, suppliers, pricing and your files.
Contact usLast updated 6 November 2026How do I convert a STEP file to IGES?
Upload your .step or .stp file to the converter at the top of this page and download one IGES file with the exact geometry in millimetres. FreeCAD, which is free, can also open a STEP and export IGES. Marathon OS is the paid route if you don't have CAD at hand: first 2 files free, then 1 credit per file.
Is the Marathon OS STEP to IGES converter free?
First 2 files free, any size up to 300 MB. After that, 1 credit per file. Credit packs bring it down to $1.80 per file. Prices include tax, you pay only when you click Download and credits never expire.
Can I convert STP to IGES?
Yes. .stp is the short extension for STEP; both convert the same way.
What is the difference between IGS and IGES?
None. .igs and .iges are two extensions for the same format, and IGES readers accept both.
Will the IGES open as a solid?
It can. Closed solids are written in IGES B-rep mode (entity type 186) when they pass our read-back check, and programs that read that mode open them as solids. If the check would lose a solid or too many faces, or the STEP holds surfaces, you get trimmed surfaces (type 144) to knit in your CAD program. Open the file to see which you got.
Does STEP to IGES lose geometry?
No. Curves and surfaces stay exact; nothing is meshed. What our IGES drops is everything around the geometry: part names, colours, the assembly tree and PMI.
What units does the IGES use?
Millimetres, stored in the file.
Do I get a quality report?
Yes. Every conversion comes with a free quality report with 11 checks, including the number of solids and faces, whether the solids are closed and whether the volume matches the STEP.
Should I send a supplier STEP or IGES?
STEP, if they accept it: it's the current standard, and our IGES doesn't carry names, colours or the assembly tree. Send IGES when their CAM or CAD system asks for it.
Can I convert an assembly?
Yes. Every part comes across in its assembled position, but as one model without the assembly tree or part names.
Can I convert IGES back to STEP?
Yes. Our IGES to STEP conversion keeps the geometry exact.
Which STEP versions are supported?
STEP files from any CAD program that writes AP203, AP214 or AP242, as .step or .stp, up to 300 MB.
Do I need an account?
To upload your own file, sign in with Google or an emailed code. The sample file works without signing in.
How long does a STEP to IGES conversion take?
It depends on the part. Large assemblies can take several minutes, and we email you when the file is ready.
Are my STEP files private?
Uploads and downloads use HTTPS. Uploaded and converted files are deleted automatically after 7 days, and converted files aren't added to the public CAD library unless you publish them. You keep ownership of your design. See the Privacy Policy.
Convert your STEP file to IGES
Exact IGES geometry in millimetres, for CAM, suppliers and older CAD. First 2 files free, any size up to 300 MB. After that, 1 credit per file.
Pricing
Pay as you go, cheaper by the pack
Your first 2 CAD file conversions are free, any size up to 300 MB, including the download. From conversion 3 on, each file costs 1 credit or a one-time payment, charged only when you click Download. 1 credit downloads any file up to 300 MB, and credits never expire.
Starter
3credits
$7.99
$2.66 each
3 downloads of any size. Good for a one-off project.
Pro
5credits
$12.99
$2.60 each
5 downloads of any size. The everyday choice.
Team
10credits
$19.99
$2.00 each
10 downloads of any size. Best balance of price and volume.
Studio
15credits
$26.99
$1.80 each
15 downloads of any size. Lowest price per file.
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