How the weight is calculated
A printed part is a solid skin with a partly hollow inside. The walls and the top and bottom layers are printed solid; the space inside them is filled at your infill percentage. The calculator treats the part as a box, works out the volume of the skin and the inside separately, and adds them.
For shapes that are not boxes, enter the dimensions of a box with the same volume, or use the weight your slicer reports. The estimate is usually within 10–15% of the slicer for box-like parts.
Worked example: a 40 mm cube
A 40 × 40 × 40 mm PLA cube with 2 walls of 0.45 mm, 4 top and bottom layers of 0.2 mm, and 20% infill:
- Shell (walls + top/bottom)
- 7,965 mm³
- Inside: 38.2 × 38.2 × 38.4 × 20%
- 11,207 mm³
- Printed volume
- 19,172 mm³
- Weight at 1.24 g/cm³
- 23.8 g
The same cube printed solid weighs 79.4 g. At 20% infill it uses 70% less plastic.
How much infill do you need?
| Use | Typical infill | Notes |
|---|---|---|
| Display models, figures | 5–15% | Walls give the strength; infill only supports the top |
| Everyday functional parts | 15–25% | A good balance of strength and material |
| Brackets, mounts, tools | 30–50% | Add walls before adding infill |
| Parts under heavy load | 50–100% | Consider a stronger material instead |
Walls usually add more strength per gram than infill. Going from 2 to 4 walls often makes a part stronger than doubling its infill, and costs less plastic.
Frequently asked questions
Does 20% infill mean the part weighs 20% of solid?
No. The walls and top and bottom layers are printed solid, so a part at 20% infill weighs much more than 20% of a solid one. For small parts the shell can be most of the weight.
Which infill pattern is strongest?
Gyroid and cubic give similar strength in all directions. Grid and lines are quicker but weaker in some directions. The pattern changes weight only slightly at the same percentage.
Why is my small part almost solid at 10% infill?
Small parts are mostly shell. A 10 mm cube with 2 walls and 4 top and bottom layers has very little inside left to fill, so infill barely changes its weight.
How do I turn weight into cost?
Enter your filament price per kg and the cost appears under the weight. For the full cost including electricity and wear, use the print cost calculator.
Last reviewed October 2026. See how we calculate.