Skip to content
Kenerate IconKenerate Icon
Kenerate AI
Start

11 shapes · real dimensions · free

STL shape generator exact sizes in mm

Need a 20 mm cube, a spacer, a ring or a dome? Pick a shape, type its dimensions in millimetres and download a print-ready STL — no CAD needed.

  • Box, cylinder, tube, cone, sphere…
  • Every dimension in mm
  • Smoothness you control
  • Sits flat on the bed

Updated by the

Quick answer

Updated

What is an STL shape generator?

An STL shape generator is a tool that makes basic 3D shapes, or primitives, as printable files with exact dimensions. Kenerate's free generator builds 11 shapes in your browser, from boxes and cylinders to spheres, tori and stars. Set the size in millimetres, check it in 3D and download STL, 3MF, OBJ or GLB, flat on the bed.

Key facts

Price
Free, no account
Shapes
Box, rounded box, cylinder, tube / ring, cone, pyramid, sphere, dome, torus, hex prism, star
Dimensions
1–250 mm per parameter
Smoothness
8–128 segments for round shapes
Placement
Centred, flat on Z = 0
Output
STL, 3MF, OBJ, GLB

Why this tool

Simple shapes, exact sizes

Many “shape generators” make pretty renders without dimensions. Here every number is a millimetre.

  • Simple 3D printed geometric shapes on a print bed

    Real dimensions

    Width, depth, height, diameters and wall sizes in mm — what you type is what prints.

    Try it
  • A 3D printer nozzle printing a grey dragon miniature layer by layer

    Spacers, rings and tubes

    Set an outer and inner diameter for washers, spacers, bushings and napkin rings.

    Try it

Also

What else it does

  • Smoothness control

    More segments make rounder curves and bigger files; 64 is plenty for most prints.

  • Combine in your slicer

    Load several shapes and arrange them — or use them as modifiers and negative volumes.

How it works

How the shapes are built

Parametric geometry in your browser.

  • Pick

    Each shape has its own parameters — size, height, inner diameter, points.

  • Generate

    The mesh is generated from those numbers with your chosen smoothness.

  • Orient

    It's turned Z-up, centred and placed on the bed.

  • Export

    STL, 3MF, OBJ or GLB downloads instantly.

How to

How to use the STL Shape Generator

Time needed
Steps
4 steps

  1. Step 1

    Choose a shape

    Box, cylinder, tube, cone, sphere, torus, star…

  2. Step 2

    Type dimensions

    Set each size in mm with the sliders.

  3. Step 3

    Set smoothness

    Raise segments for round shapes if you'll print them large.

  4. Step 4

    Download

    Save STL or 3MF and print.

Watch the tour · 1:48

Text, photo or multi-view to a textured GLB, nine engines, the viewer & lighting, compare engines, gallery, download & chat

Chapters

Who uses it

What people make

  • Calibration prints

    A 20 mm cube to check dimensions.

  • Spacers and washers

    Tubes and rings at exact sizes.

  • Teaching geometry

    Solids for maths lessons.

  • Building blocks

    Primitives to combine in CAD or a slicer.

File formats

The formats this tool reads and writes

What each file can hold, what it can't, and where it opens. Facts link to the format's own spec or reference page.

The formats this tool reads and writes — checked 2026-10-01
.stl · STL.3mf · 3MF
Full nameStereolithography3D Manufacturing Format
Made by3D Systems, 19873MF Consortium, 2015
KindTriangle mesh (binary or ASCII)ZIP package with XML
HoldsTriangle surfaces, Facet normalsMeshes with units (millimetres), Colours and materials, Several objects and build plates
NoColour and textures, Units, MaterialsAnimation
Best for3D printing — every slicer opens itModern 3D printing and multi-colour prints
Opens inCura, PrusaSlicer, Bambu Studio, OrcaSlicer, BlenderBambu Studio, PrusaSlicer, OrcaSlicer, Cura, Windows 3D Builder

Sources: Wikipedia — STL (file format) · 3MF Consortium — 3MF specification

No file yet?

Make the model first — from one photo

Every sample in the tool above began as a single picture and was turned into a 3D model in the Kenerate 3D Studio. The engine is named on each one.

Example uses

How creators use the STL shape generator

Illustrative examples of typical workflows, not customer reviews.

  • Three 3D printed calibration cubes beside a printer

    Printer owner

    A printer owner can print a 20 mm cube and measure it to check the printer's accuracy.

  • White 3D printed geometry solids on a classroom desk

    Maths teacher

    A teacher can print a set of solids such as a cone, pyramid, sphere and hexagonal prism for geometry lessons.

  • 3D printed spacer fitted on a bolt in a shelf bracket

    Home repairer

    Someone fixing things at home can print a ring or tube at an exact diameter as a spacer.

FAQ

STL Shape Generator questions

How do I make a 20 mm calibration cube?

Choose Box and set width, depth and height to 20 mm, then download. Measure the print with calipers to check your printer's accuracy.

Link to this answer

What does smoothness (segments) do?

Round shapes are made of flat facets. More segments give smoother curves and larger files; 64 is smooth at most sizes, 128 for large parts.

Link to this answer

Can I make a hollow cylinder?

Yes — use Tube / ring and set the inner diameter smaller than the outer one.

Link to this answer

Can I combine shapes?

Load several into your slicer and arrange them, or combine them in CAD. This tool makes one shape at a time.

Link to this answer

Do spheres need supports?

Usually, below the equator. Print a Dome (flat-bottomed half sphere) instead if you can.

Link to this answer

How do I make an STL file?

For simple solids, pick a shape here, type its sizes in millimetres and download. For anything else, export STL from CAD or Blender, convert another 3D file with the free converters, or generate a model with AI in the Kenerate 3D Studio (any paid plan or credit pack) and convert it.

Link to this answer

Is it free?

Yes, with no account.

Link to this answer

In depth

STL Shape Generator, explained

Facets, file size and printing simple solids well.

On this page

Facets and file size

STL stores flat triangles, so curves are approximated [1]. Doubling the segment count roughly doubles the triangles of a cylinder and quadruples those of a sphere. Beyond what your nozzle can resolve, extra segments only grow the file.

Keep going

Other 3D viewers and converters

By Last updated and reviewed

We build the Kenerate 3D Studio and these free tools. They run on three.js in your browser, so files stay on your device; every sample model is a real output of the AI engine named on it. Technical facts link to their specs and manuals.

Sources: Wikipedia — STL (file format) · Wikipedia — Wavefront .obj file · Wikipedia — FBX · Khronos Group — glTF · 3MF Consortium — 3MF specification · Wikipedia — Universal Scene Description (USD / USDZ) · Wikipedia — PLY (file format) · Khronos Group — glTF 2.0 specification · Apple — AR Quick Look · three.js — documentation · Prusa Knowledge Base — Modeling with 3D printing in mind · Prusa Blog — lithophanes and filament transparency · Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA · Wikipedia — Lithophane · W3C — CSS Values and Units Level 3 (absolute lengths) · Adobe Substance 3D — OpenGL vs DirectX normal maps · Blender Manual — Normal Map node · Wikipedia — Normal mapping · SIL Open Font License

Try the STL Shape Generator

Free and private — your files never leave your device. Want to make models with AI? That's the 3D Studio, on any paid plan or credit pack.

Make a shapeAll 3D tools

Tried it? Tell us how it went