The free STL Hollow Tool — Hollow Out Models & Save
Hollow out an STL with a wall thickness you choose, optionally add a drain hole, and see how much resin you save and what it costs.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
A 20 mm cube hollowed with a 2 mm wall has a shell volume of 3.9 cm³ instead of 8 cm³ — about 51% saved. A 30 cm³ bust with 1.5 mm walls typically uses 35–45% of the solid volume.Open the STL Hollow Tool — Hollow Out Models & Save
Illustration. Open the tool for the real thing.
See it in action
The STL Hollow Tool — Hollow Out Models & Save with sample data entered and the result showing.
What is the STL Hollow Tool — Hollow Out Models & Save?
Resin is expensive, and a solid miniature or bust wastes most of it in the interior. Hollowing creates an inner cavity so only a shell of your chosen thickness is printed. This tool builds the cavity by offsetting the surface inwards: each vertex moves along a normal computed from its neighbouring faces so that corners keep a uniform wall thickness, and the cavity is added as an inside-out inner shell. You choose the wall thickness (0.4–8 mm) and see volume and resin cost before and after.
A hollow part needs a way for uncured resin to escape. Tick the drain-hole option and a hole of your chosen diameter is cut through the lowest point of the part with a boolean cut. Use the viewer's section tool to inspect the wall. The tool also checks the cavity volume against the expected shell volume and warns when thin features make the offset overlap itself.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Angle-weighted normal solve keeps corners at the chosen wall thickness.
A through-hole at the lowest point, boolean-cut in the browser (up to 40k triangles).
Volume, grams, cost and percent saved.
Slice through the model to see the walls.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
How it compares
A plain look at this tool next to the usual alternative.
| This 3d tool | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
Is the cavity wall thickness exact?
It is exact on flat faces and at convex corners; on very sharp concave details the offset can overlap, which the check reports.
Do I still need a drain hole in my slicer?
If you tick the drain hole here no, otherwise yes. Resin slicers also have hole tools.
What happens to the original file?
Nothing — your file is not modified or uploaded; you download a new file.
Does it work for FDM?
It works, but FDM slicers hollow with infill, which is usually better.
How do I use the STL Hollow Tool — Hollow Out Models & Save?
1. Drop in a watertight STL. 2. Choose wall thickness and drain-hole size. 3. Press Hollow and inspect with the section tool. 4. Download the hollow STL and slice it.
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Try the STL Hollow Tool — Hollow Out Models & Save now
Hollow an STL with a set wall thickness and a drain hole, see resin saved. Free to use.
Try it free