OBJ to STL Converter

Turn an OBJ from a model site into a binary STL your slicer can open, entirely inside 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

Your OBJ becomes a printable STL in three local steps.

  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

Downloaded OBJ models often become physical objects at the printer. These are six common destinations for the finished STL.

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

OBJ can describe more than the triangle shell that STL receives. This conversion keeps the mesh geometry and writes it as binary STL, while colour, materials, textures, names and hierarchy fall away. Numeric coordinates pass through unchanged because neither format declares a unit. Check the reported triangle count, object count and bounding box before you save the result.
GeometryColourMaterialsUnitsTopologyFile size

Geometry

Faces from the OBJ become triangles in the binary STL. The visible shape carries through as mesh geometry, without the surrounding OBJ structure.

OBJ file format

the file you have

Opolyo

this page

Your OBJ geometry becomes slicer ready binary STL

INSIDE THE CONVERSION

How OBJ to STL Conversion Builds the Output

The browser does more than rename the extension. It reads the loaded surface, resolves it into triangles, applies object transforms and writes a new binary file.

  1. 01

    Polygon faces become STL triangles

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

    Each final triangle is written with three vertices and a freshly calculated face normal. The result describes the same loaded surface in the compact binary structure that slicers read.

  2. 02

    Every loaded object contributes geometry

    The exporter walks every mesh that the OBJ loader found and writes all of their triangles into one STL file.

    Object names, groups and hierarchy are not part of STL, but their transformed surfaces still contribute to the output. The object count shown above the button tells you how many meshes entered that pass.

  3. 03

    Coordinate numbers stay unchanged

    OBJ and STL both leave units undefined, so this route copies the loaded dimensions without applying a scale factor.

    A coordinate value of 25 remains 25 in the STL. Your slicer decides whether that number means millimetres, which makes the displayed bounds more useful than an assumed conversion factor.

  4. 04

    The bounds are the scale checkpoint

    The browser calculates the full bounding box before it creates the download.

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

SPECIFICATIONS

OBJ to STL Specifications

The conversion transfers triangle geometry and coordinate numbers from OBJ into binary STL.

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

Compare the browser workflow with common conversion habits at the point where your slicer rejects OBJ.
File handling
Most tools:Many online tools upload the source file before processing.
Opolyo:Opolyo processes your OBJ entirely inside the active browser tab.
Access
Most tools:Many services often place registration before the download step.
Opolyo:You convert and download without creating an account.
Usage
Most tools:Many web converters often restrict daily or monthly conversion counts.
Opolyo:You can process any number of files, with a 100 MB limit for each file.
Scale
Most tools:Many pipelines often assume a unit when moving OBJ geometry into a slicer format.
Opolyo:Opolyo leaves all coordinate numbers unchanged because OBJ and STL declare no unit.
Inspection
Most tools:Many quick converters often provide the result without a geometry summary.
Opolyo:You see triangle count, object count and bounding box before the download.
The 100 MB boundary protects the memory available to your browser tab. Files within that boundary incur no per file processing cost. The converter at the top of this page does it without an account.

WHAT YOU GET

STL ready models you can spin right here

Choose an OBJ and inspect the geometry summary produced locally. Download the binary STL once the counts and bounding box match the model you intended to convert.

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 that a slicer can import.

  • The coordinate numbers remain identical during conversion. OBJ and STL declare no unit, so the converter does not guess or change the scale.

  • The converter reads the objects present in the file and reports their count. Their triangle geometry is written into the STL result.

  • They are not included. OBJ uses a separate MTL sidecar for materials, this converter does not write one, and STL has no material or texture fields.

  • Yes. The loaded OBJ surface is resolved into triangles before binary STL is written. Slicers receive the resulting triangle mesh.

  • Yes, browser conversion is free because it runs on your own machine and creates no processing cost per file. You do not spend credits.

  • No account is required. You can open the converter and use it immediately.

  • There is no cap on file count. The size limit is 100 MB for each selected file because larger data can exhaust the tab memory.

  • No. Three.js reads the OBJ within your browser tab, and conversion remains on your device.

  • Your current browser session performs the work. The file does not enter an upload or server processing queue.

  • You can review the detected triangle count, object count and bounding box. The download follows that inspection.

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

  • The result is binary STL. Its geometry comes from the triangles read in your OBJ.

  • Their geometry is included, but STL stores one flat triangle list rather than OBJ group names or hierarchy. Use the object count before download to confirm that every expected mesh loaded.

  • Format conversion writes the loaded surface into STL. Check the result with your slicer's mesh validation before printing, and use its repair tools when the source has holes or intersecting faces.

  • Yes, the paid Opolyo product can generate a 3D model from one photograph or a written description. Generation runs on GPUs and costs credits, while this local OBJ conversion remains 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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Start with your OBJ

Convert the file locally, or generate a fresh 3D model with paid AI tools.

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