# IGES to STL Converter

> Turn IGES (.iges, .igs) CAD files into STL for printing, meshed in your browser with OpenCascade, with a check for the gaps IGES surfaces often leave.

Page: https://printpal.io/convert/iges-to-stl
Updated: 2026-11-12
Use it: open https://printpal.io/convert/iges-to-stl in a browser and drop a file. Free, no account, files are processed locally and never uploaded.

IGES often stores surfaces rather than solids: faces that look closed but don't share edges. The converter meshes every surface with OpenCascade and writes them into one STL in millimetres. If the surfaces didn't close, the STL has open edges where they meet.

Open the result in the [STL viewer](https://printpal.io/tools/stl-viewer) to check: zero open edges means it will slice cleanly. If not, sew the surfaces in your CAD tool, or try [Mesh Repair](https://printpal.io/tools/mesh-repair) on the STL.

## How to convert IGES to STL

1. **Drop your IGES files.** Drop .iges or .igs files. The CAD reader (about 7 MB) downloads the first time.
2. **Check the preview.** The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.
3. **Choose STL options.** Binary STL by default (smallest, read everywhere). Tick ASCII only if an old tool asks for text STL.
4. **Convert and download.** One file downloads straight away. A batch gives a download per file and one .zip of all of them.

## What carries over

| | Result |
|---|---|
| Geometry | Exact IGES surfaces are tessellated into triangles with OpenCascade at the quality you pick (Draft, Normal or Fine). |
| Color | Dropped: STL cannot store color. |
| Units | Converted from the declared unit to millimetres, so it keeps its real size. |
| Orientation | Both are Z up, so it stays the right way up. |
| Objects | Merged into one surface: STL has no objects. |
| Editability | Feature history and exact surfaces are not recoverable from a mesh. Keep the CAD file as your master. |

## IGES at a glance (Initial Graphics Exchange Specification)

IGES was first published in 1980 and is still the lowest common denominator between CAD and CAM systems. It often carries loose surfaces rather than closed solids.

- **Stores:** Curves and trimmed surfaces, sometimes solids
- **Color:** Per entity, rarely used
- **Units:** Declared in the file
- **Up axis:** Usually Z
- **Meshing:** Needs tessellation; surface models may not close into solids
- **Opens in:** Most CAD and CAM systems

## STL at a glance (Stereolithography (Standard Triangle Language))

Created by 3D Systems in 1987 for the first stereolithography printers, STL is still the format every slicer and print service accepts. It describes a surface as a list of independent triangles, with no shared vertices, units, colors or scene structure.

- **Stores:** Loose triangles: three corners and a normal each, binary or ASCII
- **Color:** None in the standard
- **Units:** None written; slicers assume millimetres
- **Up axis:** Z, the slicer convention
- **File size:** 50 bytes per triangle in binary, about 5 times that as ASCII
- **Opens in:** Every slicer, CAD tool and 3D app

## Tips

- **Ask for STEP** If whoever sent the IGES can export STEP, ask. STEP keeps solids, and [STEP to STL](https://printpal.io/convert/step-to-stl) gives a cleaner mesh.
- **Quality** Use Fine for small details; Draft for big surface models you only need to check.
- **Units** IGES declares its unit, and the STL comes out in millimetres.

## FAQ

### Can I convert IGS to STL too?

Yes. .igs and .iges are the same format.

### Why does my STL from IGES have holes?

The IGES surfaces only appear to meet. Sewing them into a solid in CAD fixes the cause; Mesh Repair can close small gaps.

### Is my file uploaded?

No. OpenCascade runs in your browser as WebAssembly.

### Is the converter free? Are there limits?

Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

### Are my files uploaded?

No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.

## Related

- [STL to OBJ Converter](https://printpal.io/convert/stl-to-obj)
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- [STEP to STL Converter](https://printpal.io/convert/step-to-stl)
- [3D model viewer](https://printpal.io/tools/3d-model-viewer)
- [3D model converter](https://printpal.io/tools/3d-model-converter)
- [Mesh Repair](https://printpal.io/tools/mesh-repair)
- PrintPal for LLMs: https://printpal.io/llms.txt