Convert IGES to STL
IGES is the CAD exchange format from before STEP, and files in it are still handed around manufacturing every day. Converting one to STL works, but IGES has a habit STEP does not, and knowing about it beforehand saves an afternoon: an IGES file is often a bag of separate surfaces rather than a solid.
Drag a 3D file here, or.
This page is set up for IGES files. Other formats we can read work here too.
The file is read on your own computer. It is never uploaded.
Your file is read by your own browser and never sent to a server. There is no upload, no account and no copy of your model anywhere but on your computer.
IGES stores surfaces, and sometimes only surfaces
A STEP file describes a solid: a closed volume with an inside and an outside. An IGES file describes surfaces, and whether those surfaces happen to enclose a volume is not something the format insists on.
Well-made IGES files do enclose one, and convert to a clean printable STL with nothing to think about. Older files, and files exported carelessly, arrive as patches with tiny gaps between them where two surfaces do not quite meet. The shape looks perfect on screen. A slicer refuses it, or slices it into something with missing walls.
That is why the measurements under the 3D view include whether the model is a closed shape. Check that line before you download. If it says the model has holes, the gaps were in the IGES file and no converter can invent the missing surfaces.
What to do when it is not closed
The best fix is not a fix at all: ask for a STEP file instead. Whoever sent the IGES almost certainly has the original model, and exporting STEP takes them fifteen seconds and solves the problem completely. STEP records solids properly and this whole class of trouble disappears.
If that is not possible, FreeCAD will open the IGES, attempt to sew the surfaces into a solid, and export a STEP or an STL. It is free, and the sewing step is exactly what it is for. Some slicers — PrusaSlicer and Cura among them — will also repair small gaps automatically when you load a mesh, which is often enough for a part with one or two bad edges.
The detail setting, and units
Like STEP, an IGES file holds exact surfaces rather than triangles, so the triangles are made during conversion and you choose how fine. Normal is right for printing; the triangle count next to the control shows what each choice costs.
IGES states its unit in the global section at the top of the file, and this tool reads it. Inches are much more common in IGES than in STEP, because of where and when the format was used, so it is worth a glance at the input unit box before converting. Set the output to millimetres and the arithmetic is handled.
Files that hold no surfaces at all
IGES is also used for two-dimensional drawings and for wireframe — curves and points with no surface anywhere. A file like that cannot become a mesh, because there is nothing to cover with triangles, and the tool will tell you so rather than handing you an empty STL.
If that happens, the file was an outline rather than a model. Go back to whoever produced it and ask for a solid.
What survives, and what does not
Kept in the STL file
- The shape, to the tolerance you choose, wherever the file holds real surfaces
- The real size, read from the unit the IGES global section declares
- Every surface in the file, merged into one body
Lost on the way
- The exact curved surfaces — they become flat triangles and cannot be turned back
- Watertightness, when the IGES surfaces did not meet in the first place
- Colour, layer names and anything else the file carried around the geometry
How to convert IGES to STL
Drop the .iges or .igs file in
Both extensions are the same format. The CAD engine downloads on the first CAD file you open — about 3 MB, once.
Read the closed-shape line under the 3D view
This is the check that matters for IGES. If the model is not a closed shape, the surfaces in the file have gaps between them and a slicer will struggle.
Check the unit
IGES states its unit in the global section and inches are common. The input unit box shows what the file declared — correct it if you know it is wrong.
Choose the detail
Normal for printing. Fine if a curved surface will be visible on the finished part. Watch the triangle count change as you switch.
Convert, or go back for a STEP file
If the model was closed, download the STL and print it. If it was not, ask the sender for a STEP file — that fixes the cause rather than the symptom.
IGES and STL compared
| Property | IGES.iges .igs | STL.stl |
|---|---|---|
| File contents | Plain text in fixed 80-character records, divided into five labelled sections. | Binary or plain text. Binary is an 80-byte header, a triangle count, then 50 bytes per triangle. |
| Geometry | Exact surfaces and curves, often as unstitched trimmed patches rather than a solid. | Triangles only. Curves are approximated when the file is made, and cannot be recovered. |
| Units | Recorded in the global section, as one of eleven fixed unit codes. | None. The file stores bare numbers, and every reader has to guess what they mean. |
| Colour and texture | A colour number per entity, from a small fixed palette. | None. There is no place in the format for a colour, a material or a texture. |
| Separate objects | Flat. Assembly structure is weak and frequently lost. | One body. Several parts written into one STL become one undivided lump of triangles. |
| Published by | The US National Bureau of Standards, 1980. Frozen at version 5.3 in 1996. | 3D Systems, 1987, for the first stereolithography machines. |
| Written by | Older CAD systems, and current ones when a customer asks for it. | Every CAD program and every slicer, as the common denominator. |
Questions
- Is .igs the same as .iges?
- Yes. Two extensions for one format, from a time when three letters was a limit. This page reads either.
- The model has holes. Is that this tool’s fault?
- No — it is in the IGES file. IGES stores loose surfaces and does not require them to meet exactly, so gaps are common. No converter can invent the missing surface. Ask for a STEP file, or sew the surfaces in FreeCAD.
- IGES or STEP?
- STEP, for anything new. IGES is from 1980 and frequently delivers unstitched patches instead of a solid, which means repair work at the other end. Use IGES only when the receiving software genuinely cannot take STEP.
- Nothing appeared and it said there were no surfaces. Why?
- The file holds only curves and points — a wireframe or a 2D drawing rather than a model. There is nothing to cover with triangles. The person who sent it needs to export a solid.
- My part is twenty-five times too small. What went wrong?
- The file was in inches and something read it as millimetres. Check the input unit box against what the file declared and set the output to millimetres.
Having it printed
If the part is larger than your bed, needs a material your printer cannot handle, or you do not have a printer, these will print it and post it to you. Work out what it would cost you first — the cost calculator on this site gives you a figure to compare against.
- JLC3DPCheapest for resin and nylon, slow shipping
- CraftcloudCompares dozens of printers at once, including local ones
- PCBWayMetal printing and CNC as well as plastic
These are ordinary links, not paid referrals — we earn nothing if you use them. The converter above is the same whether you do or not.
Where to go next
Other things to do with a IGES file
Other ways to get a STL file
Related guides and tools
- Gridfinity generatorBins and baseplates, any size, built in the browser
- Turn text into an STLType a word and print it, without drawing anything
- Turn an image into an STLA photo or a logo, turned into something you can print
- Lithophane generatorA photo printed as thickness, lit from behind
- Repair an STL that will not sliceClose the holes and separate the bad edges so a slicer accepts it
- STL to G-codeGuide
- How to convert an STL file to G-codeGuide