OBJ to STL Converter

Convert an OBJ from a model site into a binary STL your slicer opens, in your browser.

Your file never leaves this browser. No account, no upload, no limit on how many you convert.

HOW IT WORKS

How to Convert an OBJ File to STL

Pick the OBJ, check what the browser read, download a binary STL.

  1. Choose your OBJ

    Select an OBJ file up to 100 MB from your device.

    Nothing leaves your browser

  2. Inspect the geometry

    Review the triangle count, object count and bounding box read from the file.

    Check before conversion

  3. Download binary STL

    Convert the mesh and save the binary STL for your slicer.

    Numbers stay unchanged

What People Print From an OBJ

An OBJ downloaded from a model site usually ends up as one of these prints. These are the common next steps for the converted file.

Tabletop Miniatures

You print heroes, monsters and terrain pieces for tabletop games.

Generate a model from a photo

Replacement Parts

You turn downloaded knobs, clips, brackets and covers into usable spares.

GLB to STL converter

Cosplay Props

You produce masks, armour sections and handheld accessories for a costume.

Describe a model in words

Architectural Models

You build scaled structures, room layouts and site models for physical review.

STL to OBJ converter

Display Pieces

You make statues, busts and decorative objects for a shelf or exhibition.

3D model converter

Functional Prototypes

You test the fit and shape of an enclosure, mount or mechanical component.

FBX to OBJ converter

opolyo-model.glb @ in about two minutes

What Survives .obj to .stl

STL stores a triangle surface, so that is what comes out: the mesh geometry, written as binary STL with the coordinate numbers unchanged. Colour, materials, the MTL sidecar and object names stay in the OBJ.
GeometryColourMaterialsUnitsTopologyFile size

Geometry

Faces from the OBJ become triangles in the binary STL. The shape carries through as mesh geometry only.

OBJ file format

the file you have

Opolyo

the converter above

Your OBJ geometry becomes slicer ready binary STL

INSIDE THE CONVERSION

How OBJ to STL Conversion Builds the Output

The browser turns an OBJ into a binary STL in four stages. Each stage below says where the triangles, the coordinates and the final file come from.

  1. 01

    Polygon faces become STL triangles

    The OBJ loader resolves the visible surface into triangles before the STL writer runs.

    Each triangle is written with three vertices and a freshly calculated face normal. The result is the same surface in the binary form slicers read.

  2. 02

    Every loaded object contributes geometry

    Every mesh the loader finds goes into one STL file.

    Object names, groups and hierarchy are not part of STL, but their transformed surfaces are. The object count above the button tells you how many meshes went in.

  3. 03

    Coordinate numbers stay unchanged

    OBJ and STL both leave units undefined, so the loaded dimensions are copied without a scale factor.

    A coordinate of 25 stays 25 in the STL. Your slicer decides whether that means millimetres, so check the displayed bounds.

  4. 04

    The bounds are the scale checkpoint

    The full bounding box is calculated before the download is created.

    Compare those three dimensions with the size you expect in the slicer. An unexpected value usually points to a unit choice in the source, and the triangle and object counts confirm the whole model loaded.

SPECIFICATIONS

OBJ to STL Specifications

Reads OBJ geometry and writes it as binary STL with the coordinate numbers unchanged.

Input

Accepts
.obj
Size ceiling
100 MB
Read in
Your browser

Output

Writes
Binary STL
Topology
Triangles
Colour
Not stored

Scale and cost

Scale
Carried through
Conversions
Unlimited
Price
Free

BEFORE YOU CONVERT

Why Opolyo, not a typical OBJ to STL converter

The difference shows at the moment your slicer rejects the OBJ.
File handling
Most tools:Often uploads the OBJ to a server before processing.
Opolyo:Processes the OBJ inside your browser tab.
Access
Most tools:Often puts registration before the download step.
Opolyo:Converts and downloads without an account.
Usage
Most tools:Often caps daily or monthly conversions.
Opolyo:No file count cap, up to 100 MB per file.
Scale
Most tools:Often assumes a unit when moving OBJ geometry into a slicer format.
Opolyo:Leaves every coordinate unchanged, since OBJ and STL declare no unit.
Inspection
Most tools:Often delivers the result without a geometry summary.
Opolyo:Shows triangle count, object count and bounding box before the download.
Files up to 100 MB convert in your browser at no cost. The converter above does it without an account.

WHAT YOU GET

STL ready models you can spin right here

The models below were made with Opolyo. Drag one to spin it. What you download above is the same kind of file: a real mesh, ready for the slicer.

Pricing

Every credit turns into a model you keep

Billed every month. Cancel anytime.

Start

For your first prints and props

$19.99

USD

Billed monthly

  • 160 credits / month (16 generations)
  • Standard and Ultra PBR textures
  • GLB, STL & OBJ export
  • Built-in format converter
  • Failed generations refunded automatically
  • Commercial license
  • Email support
Get Opolyo

Cancel anytime.

POPULAR

Build

For people who ship models weekly

$39.99

USD

Billed monthly

  • 360 credits / month (36 generations)
  • Standard and Ultra PBR textures
  • GLB, STL & OBJ export
  • Built-in format converter
  • Failed generations refunded automatically
  • Commercial license
  • Email support
Get Opolyo

Cancel anytime.

BEST VALUE

Scale

For studios and print farms

$89.99

USD

Billed monthly

Everything in Build, plus:
  • 900 credits / month (90 generations)
  • Lowest cost per credit
  • Priority email support (24h response)
Get Opolyo

Cancel anytime.

I filled my first map in just one afternoon! That's 24 props already.

Marcus Reed

Built a Game

OBJ to STL Converter FAQ

Question not here? Ask by email.

  • Yes. The converter reads the OBJ geometry and writes a binary STL a slicer can import.

  • Yes. OBJ and STL declare no unit, so the coordinate numbers are copied unchanged.

  • Yes. It reads every object in the file, reports the count, and writes all of their triangles into the STL.

  • They are dropped. OBJ keeps materials in a separate MTL sidecar, and STL has no fields for materials or textures.

  • Yes. The loaded surface is resolved into triangles before the binary STL is written.

  • Yes. It runs on your own machine, so it is free and uses no credits.

  • No. Open the converter and use it straight away.

  • No limit on how many files. Each file can be up to 100 MB.

  • No. The browser reads the OBJ in the tab and the conversion stays on your device.

  • In your browser tab. The file never enters an upload or server queue.

  • Triangle count, object count and bounding box. Check them before you download.

  • No. STL stores a triangle list and has no colour, texture or material data.

  • Binary STL, built from the triangles read in your OBJ.

  • Their geometry is included, but STL stores one flat triangle list with no group names or hierarchy. Use the object count before download to confirm every expected mesh loaded.

  • No. It writes the loaded surface as it is. Run your slicer's mesh check before printing and use its repair tools if the source has holes or intersecting faces.

  • Yes. The paid side of Opolyo generates a 3D model from one photo or a written description, and that uses credits. Converting an OBJ you already have stays free.

What people make with Opolyo

5,873 makers and counting. A few of them told us what they made, and what happened next.

  • The customer's payment dashboard, a net revenue panel reading $2,605.00 with $0.00 for the comparison period
    I’m a game dev and originally started using this to turn some of my reference images into 3D assets for a project. A few of the models turned out better than I expected, so I cleaned them up and started selling them on the side too. Just crossed $2,600 in net revenue from those 3D models. Never really planned on becoming an asset seller, but I’m definitely not complaining 🙌
    N
    Nathan Brooks
  • Didn’t think a single image would get me this far. The model needed a little cleanup, but I had a solid base ready in minutes. Saved me an entire afternoon.
    D
    Dylan Reeves
  • Turned one of my kid’s drawings into a little 3D character with Opolyo. She absolutely lost it when she saw it. Probably the most fun thing I’ve made with this so far.
    K
    Kyle Brandt
  • The customer's Stripe gross volume: £231.05 for Sep 2025 to Aug 2026 against £0.00 for the twelve months before, the line flat at zero until a single month of £186.15 near the end
    Honestly didn’t expect anyone to actually pay for the 3D stuff I was making. Put a few of them up for sale just to test it and somehow made £231 from my models. Still feels a bit unreal seeing that number 😂
    O
    Owen Whitaker
  • The customer's Dodo Payments record of paid 3D requests, at a range of different amounts
    I started using Opolyo for a few custom 3D requests from clients and somehow it turned into a little side service of its own. Some people just need a quick conversion, others want more detailed work, so the order sizes are all over the place. Seeing multiple paid requests come in on the same day still feels pretty surreal. Never thought image-to-3D would become something clients actually kept coming back for.
    A
    Adam Pike
  • I use a lot of reference images when working on interior concepts, and this made it really easy to turn an object I liked into a rough 3D asset. I still adjusted a few things afterward, but it saved me from modeling the whole thing from zero.
    C
    Claire Bennett
  • Couldn’t find the exact prop I needed anywhere, so I threw the reference image into Opolyo as a last resort. The first result wasn’t perfect, but the overall shape and proportions were already there. It actually looked like the thing in my reference. After a little cleanup, it was exactly what I needed.
    J
    Jonah Reyes
  • Used it to turn a couple of product images into 3D models for our store. Took a few tries to get the best result, but still much easier than hiring someone to model everything manually.
    G
    Grant Miller
  • The customer's inbox of Stripe payment notifications: five payments, four of $14.99 and one of $125.88
    Woke up, checked my inbox and Stripe notifications just kept showing up. Most were $14.99 orders, then a $125.88 payment landed later in the day. I’m still pretty new to selling my 3D stuff, so seeing 5 sales come in on the same day was a really nice feeling. 🔥
    M
    Miles Prescott
  • I had a photo of a small figurine from years ago that I couldn’t find anywhere anymore. Tried putting it into Opolyo just to see what would happen, and the result was honestly better than I expected. It felt like bringing an old thing back to life. I still want to clean up a few details before printing it, but this is probably my favorite use so far.
    R
    Riley Fenn
  • Turned a photo into a little 3D model, printed it, and gave it to a friend for his birthday. Wasn’t expecting him to react that much 😂 He absolutely loved it. Now I’m thinking of making a few more for Christmas.
    T
    Tyler Hodge
  • The customer's Dodo Payments dashboard for their 3D commission work, totalling $181.92
    I mostly got into this because I like 3D printing and wanted to make a few custom pieces without learning modeling from scratch. Then a couple of people asked if I could make something for them too, so I started taking small requests here and there. Just hit $181.92 from custom 3D commissions. It’s not a huge number, but getting paid for something I was already doing for fun feels pretty awesome.
    W
    Wes Delaney
  • Been playing around with this for a small game project and some of the results are actually really fun. I generated a few props from reference images and one of them ended up fitting the scene perfectly. It’s staying in the game.
    E
    Evan Ross
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