You no longer need a four-figure license — or a subscription — to do real CAD. Free and open-source tools now cover every niche. Here's the landscape, organized by what you're trying to make.

Parametric solid modeling

  • FreeCAD (desktop, open source) — the flagship. Full feature-tree modeling on the OpenCASCADE kernel, plus workbenches for drawings (TechDraw), CAM, FEM, sheet metal, and architecture. The 1.x era brought major usability fixes. Steepest learning curve on this list; most capability, too.
  • Onshape free tier (cloud) — polished professional parametrics with the caveat that free documents are public.
  • SolveSpace (desktop, open source) — tiny, fast parametric modeler with an elegant constraint system; great for simple mechanical parts and linkages.

Direct / touch-first solid modeling

  • OpenShape3D (iPad & iPhone, open source) — Shapr3D-style sketching, constraints, push/pull, fillets, and booleans on the OpenCASCADE kernel, exporting STL/3MF/OBJ/GLB/USDZ/DXF. The free way to model exact parts on a tablet.

Code-defined CAD

  • OpenSCAD — describe parts as code; unbeatable for parametric families (every Thingiverse "customizer" is OpenSCAD). Programmer-brain required.
  • CadQuery / Build123d — Python scripting over OpenCASCADE: exact B-rep from code, ideal for generated or version-controlled geometry.

Mesh modeling & sculpting

  • Blender — the open-source giant: modeling, sculpting, rendering, animation. Not exact CAD (triangles, not B-rep), but essential for art, visualization, and organic shapes.
  • Meshmixer / MeshLab — free mesh repair and cleanup before printing.

2D CAD

  • LibreCAD / QCAD community — DXF drafting for laser cutting and floor plans.
  • KiCad — while we're here: fully open-source electronics CAD, best-in-class.

Browser & education

  • Tinkercad — free, friendly boolean building blocks; the on-ramp for kids.

Building a zero-cost workflow

  1. Ideate & model on iPad: OpenShape3D for constrained sketches and direct solids, anywhere.
  2. Production features on desktop: FreeCAD when you need drawings, assemblies, or CAM.
  3. Organic & rendering: Blender.
  4. Slice & print: PrusaSlicer, Cura, or Bambu Studio (all free) via 3MF/STL.

Notice a theme: OpenCASCADE powers FreeCAD, CadQuery, and OpenShape3D alike — the open-source world has effectively standardized on one excellent kernel, which means geometry concepts (and often files) move cleanly between these tools. Learn once, use everywhere.