How to Resize and Rescale STL Miniatures for Resin Printing
How to scale STL miniatures to 28mm or 32mm, match an existing army, keep base sizes right, and avoid the detail loss and support problems that scaling causes.
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You download a great STL, print it, and it comes off the plate looking perfect. Then you set it next to the rest of your army and it is a head too tall, or it is dwarfed by the figures around it. The sculpt was fine. The scale was wrong.
Scaling is one of those steps that seems trivial (just drag a slider) and quietly causes half the “why does this look off” problems in the hobby. Get it right and a downloaded file drops seamlessly into an existing collection. Get it wrong and you either waste resin printing something the wrong size or, worse, you do not notice until it is painted and on the table.
This guide covers how to resize STL miniatures properly in Lychee and ChituBox: how to pick the right target scale, how to scale to a specific size, and the things scaling does to your model that nobody mentions until a print fails. If resin printing itself is new to you, start with the complete beginner’s guide to resin miniature printing and come back once you have a print or two behind you.
What Scale Actually Means for Miniatures
Tabletop “scale” is measured to the eye line, not the top of the head. A “28mm” figure has its eyes about 28mm off the base. Total height to the top of the head runs a few millimeters taller, and a raised weapon or banner taller still. This matters the moment you start measuring, because if you measure to the top of the head and scale to that number, you will end up a little short.
The common scales you will run into:
| Scale | Eye line | Typical use |
|---|---|---|
| 28mm heroic | ~28mm | The default for most fantasy and sci-fi wargames and DnD |
| 32mm | ~32mm | Newer Games Workshop kits and some “true-scale” sculpts |
| 54mm | ~54mm | Display pieces, busts, large character models |
| 15mm | ~15mm | Mass-battle historical and sci-fi systems |
| 6mm / epic | ~6mm | Large-scale battles, vehicles, terrain armies |
The trap inside all of this is “heroic” versus “true” scale. Heroic 28mm sculpts have deliberately oversized hands, weapons, and heads so detail reads at arm’s length. A true-scale 32mm figure is anatomically slimmer. If you scale a slim true-scale model up to match the height of a chunky heroic one, it gets taller but stays slim, so it can still look like it does not belong. Height is only half of matching a collection. Bulk and proportion are the other half, and scaling cannot fix those.
Measure First, Scale Second
Before you open the slicer, measure what you are trying to match. Pull a figure from the army, box, or game you want the new model to join and measure it to the eye line. Digital calipers make this easy, but a ruler held against the model gets you close enough for a first pass.
If you are not matching an existing collection and just want a “correct” tabletop mini, aim for 28mm to 32mm at the eye line and move on. The board game case is its own thing: matching Gloomhaven or Frosthaven components adds considerations around base fit and card-insert clearance, but the scaling mechanics below are identical.
Write the target number down. You are about to do arithmetic in a slicer and it is easy to fat-finger a field.
Scaling in Lychee Slicer
Import the STL and click the model to select it. The transform panel on the right shows Size (in millimeters) and Scale (as a percentage), with X, Y, and Z fields for each.
Lock the ratio. Confirm the chain-link icon that ties the three axes together is active. When it is, changing one value scales the other two in proportion. This is what you want almost every time.
Scale to a size. If you know the model needs to be a specific height, type that number into the Z Size field. The X and Y follow automatically. Remember the Z Size is total model height, not eye line, so add the head-to-eye difference to your target (a few millimeters) if you measured to the eye line.
Scale by percentage. If you know the ratio, type it into the Scale field instead. To calculate it from a measurement: divide your target by the model’s current size and multiply by 100. A model the slicer reports as 34mm tall, scaled to a 30mm target, is 30 / 34 x 100, which is about 88 percent.
Lychee updates the bounding box live so you can sanity-check the result before doing anything else.
Scaling in ChituBox
The workflow is nearly identical. Select the model, open the Scale tool from the left toolbar, and you get the same X/Y/Z fields with a uniform-scaling toggle.
Keep “uniform” checked. ChituBox calls the aspect-ratio lock uniform scaling. Leave it on. With it on, entering a value in one axis (or a single percentage) scales the whole model in proportion.
Set a target or a percentage. Type a target dimension in millimeters into the relevant axis, or use the percentage field. ChituBox shows the resulting size immediately.
One ChituBox habit worth having: after scaling, click somewhere to deselect and reselect the model to confirm the numbers “stuck.” The tool occasionally shows an intended value in the field before it is applied, and a quick reselect confirms the real current dimensions. The ChituBox settings guide for miniatures covers the rest of the slicer setup once your model is sized; the Lychee slicer settings guide does the same for Lychee.
What Scaling Does to the Print
This is the part that catches people out. Scaling is not a neutral operation. It changes several things at once.
Detail and wall thickness shrink with the model. Every feature scales together, including the thin ones. A sword blade that was 0.6mm thick becomes 0.45mm at 75 percent scale, and somewhere below your printer’s practical minimum it stops printing cleanly. Antennae, spear tips, individual fingers, and cloak edges are the first to go. Scaling down 10 to 15 percent is usually safe. Past about 25 percent down, inspect the thinnest parts and expect to run a test print.
Resin use scales with the cube. Double the linear size and you use eight times the resin, because volume is a cubic measure. In practical terms, 120 percent linear scale is about 1.7 times the resin, and 150 percent is about 3.4 times. This is easy to forget and expensive to learn. If you are scaling up a large model, work out the cost first: the resin cost per miniature guide has the volume-to-cost math.
Hollowing has to be redone. If you hollowed the model before scaling, that hollow cavity scaled too, and the wall thickness is now wrong. Scaling up is exactly when hollowing matters most (to control resin use and reduce suction), so re-hollow at the final size. The hollowing guide walks through drain-hole placement for the new dimensions.
Supports are invalidated completely. More on this below, because it is the mistake that costs people whole prints.
Never Trust Pre-Supported Files After Scaling
If you scale a model, its supports no longer fit. This is true for supports you generated yourself, and it is doubly true for pre-supported STL files.
A pre-supported file ships with supports carefully placed for the model at its intended size. Scale the mesh and those support tips drift away from the surface they were touching, contact points end up floating in space or buried inside the model, and islands the original supports handled reappear unsupported. The print starts, a support misses, a layer peels into the FEP, and you come back to a cloudy vat and a bare plate.
The rule is simple: delete every support after scaling and generate fresh ones at the final size. Treat scaling and supporting as one combined step. The full support placement guide covers how to do it properly for miniatures, including the manual passes on weapon tips and thin extremities that auto-supports miss.
If your print does fail after a rescale, the print failure troubleshooting guide covers how to read the wreckage and figure out whether it was supports, exposure, or the scale itself.
The Base Size Problem
Here is a subtle one. When a model has a base built into the STL and you scale the whole file, the base scales with it. Scale a figure on a 32mm integrated base up by 15 percent and the base is now about 37mm. It will not sit right in a movement tray, it breaks unit coherency spacing, and for board games it will not drop into a card slot or foam insert cut for the stock size.
If base diameter matters to you, do not scale the integrated base. Instead:
- Scale only the figure to the size you want.
- Delete or ignore the integrated base in the slicer, or trim it after printing.
- Mount the cleaned model on a separate base of the correct standard diameter (25mm, 32mm, 40mm, whatever your system uses).
This keeps the figure at your target scale while the footprint stays standard. It is an extra step, but it is the difference between a model that ranks up with the rest of the unit and one that fights the movement tray forever.
Scaling Terrain and Vehicles
Miniatures are not the only thing you will rescale. Terrain and vehicles have their own quirks.
Terrain is more forgiving on detail (nobody inspects a dungeon wall for crisp fingers) but far less forgiving on resin. Scaling terrain up burns resin fast because of that cube law, and large flat surfaces create suction problems. Hollow aggressively and consider whether the piece is better split and printed in sections.
Vehicles and larger kits often need to match a specific figure scale so crew and passengers fit. Scale the vehicle to the figures, not the other way around, and dry-fit any separate crew models against the scaled hull before committing.
For finding files that scale well in the first place, the best STL sites for miniatures guide covers which sources supply clean, printable meshes, and the free DnD STL roundup is a good low-risk place to practice scaling on files that cost you nothing if you get it wrong.
Do You Even Need a Bigger Printer?
Occasionally the reason you are scaling is that a model does not fit the plate. Before you start shrinking a centerpiece to squeeze it in, check whether the fix is a different machine. A larger build volume lets you print at true scale and batch more figures per plate, which changes the math on scaling entirely. The best budget resin printer guide and the best resin printer for DnD guide cover which build volumes are worth it, though for standard 28mm to 32mm work almost any current machine is plenty.
A Clean Rescaling Workflow
Putting it together, here is the sequence I run every time:
- Decide the target scale and measure a reference figure to the eye line.
- Import the STL and note its current dimensions.
- Lock the aspect ratio.
- Scale to a target height or by percentage.
- Inspect thin features if you scaled down.
- Re-hollow if you scaled up much.
- Delete old supports and generate new ones at the final size.
- Check base diameter, and swap to a separate standard base if it matters.
- Print one test figure before filling a plate.
None of these steps is hard. The failures come from skipping one, usually the supports. Before any print session, gloves on, ventilation running, and wash solution within reach: the full PPE and ventilation setup is in the resin printing safety guide.
Get the scale right once and it becomes muscle memory. The reward is a shelf where the models you printed and the models you bought stand shoulder to shoulder and nobody can tell which is which.