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Convert OBJ to STL Online: Mesh to Mesh

Convert an OBJ triangle mesh to STL. Check scale and whether the mesh is closed; the result is not a CAD solid.

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Capabilities and limits

  • Convert an OBJ triangle mesh to STL. Check scale and whether the mesh is closed; the result is not a CAD solid.
  • Conversion preserves supported geometry rather than native parametric feature history; verify output units, completeness and geometry.
  • Files are uploaded for server processing; support depends on format, version and geometry.
  • Viewing and measuring do not require an account. Free conversion points are valid for 90 days. Sign in to convert, save files across devices or create share links.
On this page

Convert OBJ to STL for a mesh workflow that expects STL. Verify units yourself. The conversion does not repair holes or create engineering geometry.

Check the OBJ before converting

OBJ coordinates are treated as millimetres here, and textures or MTL libraries are not used. Confirm that the mesh is the model you intend to convert.

Convert OBJ to STL

Choose STL and download the triangles. The file remains a mesh. It does not gain a unit declaration or a CAD feature history.

Verify closure and scale

A known dimension confirms scale. Volume is approximate and only meaningful for a closed, consistent mesh. An open OBJ does not become a watertight solid because it was saved as STL.

Input formats: OBJ

Points: viewing and measuring are free. A new account gets 3 free conversion points; free points are valid for 90 days. One point converts one file to every output format for 30 days, and a failed or incomplete conversion uses none. See pricing.

Open this tool

General steps for uploading, viewing, sectioning, measuring, converting and exporting are explained once in How it works. This page covers what is specific to this file type.

Real CADProps screenshots

The screenshots show the English interface. Captions and instructions describe the same operations.

Convert CAD files — box.obj
Convert CAD files — box.obj

Sample source and verification

Properties — obj-to-stl.stl · 10 × 20 × 30 mm · 6,000 mm³ · 2,200 mm²
Properties — obj-to-stl.stl · 10 × 20 × 30 mm · 6,000 mm³ · 2,200 mm²

When a result needs another check

Viewing can start without an account. Conversion, account storage and share creation require signing in. Temporary files expire after the displayed retention period. Read the privacy statement for server processing and deletion, and the accuracy notes before using numerical results. Do not assume that hiding a part, clipping it or exploding an assembly changes the exported source geometry.

When a result needs another check · Input formats

Continue with a related task

Original article: CADProps · https://www.cadprops.com/tools/obj-to-stl/

A reproducible example

Convert a generated closed OBJ box measuring 20 × 30 × 40 mm to STL. Reopen the result, confirm the bounding box and check that the mesh remains closed before calculating volume.

Repository-generated samples are synthetic test models. Verify your own model's units and geometry before using results.

Supported formats
All formats and limits →

Questions about this task

Can I convert OBJ to STL online?

Yes. Upload an OBJ file, choose STL and download the mesh.

Will the STL file be a closed solid?

Only if the OBJ mesh was already a closed, consistent shell. Conversion does not fill holes or rebuild CAD solids.

How are OBJ units handled?

OBJ does not declare reliable units. CADProps assumes millimetres. Check one known dimension after conversion.

Do I need an account to convert files?

View and measure without an account. Register or sign in to convert, save files and create share links. Recipients can view shared models without an account.

Related reading

Checks that help with this file.

All guides →
Measurement

OBJ Mesh Units and Volume: Check Scale and a Closed Shell

OBJ does not declare reliable units. See how millimetres are assumed, when mesh volume is only an approximation, and why OBJ is not a CAD solid.

Read the guide →Measurement

Do STL Files Have Units? How to Fix mm vs Inch Scale

No. STL has no standard unit declaration, so 25 can mean 25 mm or 25 inches. Diagnose mm-versus-inch scale errors and verify dimensions before printing or manufacturing.

Read the guide →Troubleshooting

STL Volume Zero or Missing? Check the Mesh Is Closed

Diagnose STL files with zero, missing or unreliable volume by checking watertightness, inconsistent faces, units and export quality before calculating mass.

Read the guide →