1. Take the right measurements
Use a soft tape over the clothing you'll wear under the armor. For each part, measure the one that controls fit:
| Part | Key measurement |
|---|---|
| Helmet | Head circumference above the ears and brow |
| Chest plate | Chest circumference at the fullest point, plus shoulder width |
| Pauldrons | Shoulder width (bony tip to tip) |
| Forearm / gauntlet | Forearm circumference at the thickest point |
| Shin | Calf circumference at the thickest point |
No tape handy? A front-and-side photo scan can estimate these, but treat it as a starting point.
2. Find the file's real size
Check what unit the file was modelled in (mm, cm or inches) and read its bounding box — width (X), height (Y) and depth (Z). A wrong unit is the most common reason a part comes out 10× or 25× off.
3. Work out the target size with clearance
Armor sits outside your body, so add room: padding, foam lining, clothing and space to move. For a helmet, an inside width of roughly head circumference ÷ π plus a few centimetres is a common start. Divide target width by current width to get the scale.
4. Scale per axis, not just uniformly
If you need the part wider but not taller, scale X and Z and leave Y. Uniform scaling is fine when you're simply a smaller or larger version of the reference body — most people aren't.
5. Test before the full print
- Slice a thin ring or edge section of the scaled part and print it.
- Try it on over your undersuit; check you can raise your arms, bend and turn your head.
- Adjust by a few percent and repeat if needed.
Doing it in Armor-Sizer Studio
Enter your measurements (or scan), upload the STL/OBJ, pick the part and file unit, apply the suggested scale, fine-tune X/Y/Z, and download the resized file — or flatten it into a 1:1 foam pattern.