Infill Percentage and Strength in 3D Printing
Infill is the internal lattice a slicer builds inside a printed part, sitting behind the solid outer perimeters, and it is one of several settings, alongside perimeter count and pattern, that together decide how strong the finished part turns out.
Does more infill make a 3D printed part stronger?
Adding perimeters buys more strength per unit of time and material than adding infill, and infill pattern can matter more than infill percentage.
What does Prusa recommend for infill percentage?
Prusa's own guidance is direct: strength is mostly defined by the number of perimeters and not by infill, most models need 10 to 15 percent, and there is little sense in going above 40 percent.
This is Prusa's own published guidance for its printers and slicer settings, not a measured study.
Does infill percentage raise 3D print stiffness in a straight line?
No. A peer-reviewed study measuring PLA specimens found modulus does not rise steadily as infill percentage goes up, while perimeter count moved the number more per step than infill did.
| Infill (percent) | Modulus (MPa) | Provenance |
|---|---|---|
| 0 | 703 | Materials 16(2):695 |
| 20 | 877 | Materials 16(2):695 |
| 40 | 871 | Materials 16(2):695 |
| 60 | 995 | Materials 16(2):695 |
| 80 | 847 | Materials 16(2):695 |
| 100 | 1352 | Materials 16(2):695 |
How much does perimeter count change that same modulus?
The same study states it directly: increasing the wall perimeter count has much more effect on modulus per increment than increasing infill density does.
| Perimeters (count) | Modulus (MPa) | Provenance |
|---|---|---|
| 1 | 626 | Materials 16(2):695 |
| 2 | 720 | Materials 16(2):695 |
| 3 | 804 | Materials 16(2):695 |
What did a 2025 study measure for infill percentage in PLA tensile strength?
A 2025 peer-reviewed PLA study measured tensile strength rising with infill percentage in this dataset, from 30.75 MPa at 40 percent to 49.11 MPa at 100 percent.
| Infill (percent) | Tensile strength (MPa) | Provenance |
|---|---|---|
| 40 | 30.75 | Rogelj et al. 2025 |
| 60 | 32.94 | Rogelj et al. 2025 |
| 100 | 49.11 | Rogelj et al. 2025 |
How do perimeters change tensile strength in the same 2025 study?
In the same study, perimeter count also raised tensile strength, from 21.79 MPa at one perimeter to 32.94 MPa at three.
| Perimeters (count) | Tensile strength (MPa) | Provenance |
|---|---|---|
| 1 | 21.79 | Rogelj et al. 2025 |
| 2 | 28.59 | Rogelj et al. 2025 |
| 3 | 32.94 | Rogelj et al. 2025 |
Can print pattern matter more than infill percentage?
Yes. Two separate studies found a pattern change moved strength more than a density change did, in one case at the same infill percentage.
| Material and pattern | Infill (percent) | Tensile strength (MPa) | Provenance |
|---|---|---|---|
| ABS, line pattern | 80 | 17.46 | Pattern vs density, ABS study |
| ABS, concentric pattern | 80 | 38.95 | Pattern vs density, ABS study |
| PLA, 100 percent solid | 100 | 44.34 | Harpool et al. 2021 |
| PLA, 15 percent hexagonal | 15 | 58.25 | Harpool et al. 2021 |
What this page does not tell you
- This page compares specific lab studies and Prusa's own guidance, not a formula for your part. Geometry, load direction and material still decide the real answer for a given design.
- The infill-versus-modulus data on this page does not rise in a straight line. Read the numbers as they are measured, not as a smooth trend.
- None of this data was measured on the printers that make your part, and infill pattern and percentage were not tested together across every study on this page.
When to print a test coupon instead
Print a small test coupon at the infill percentage, pattern and perimeter count you are considering before committing to a full run, especially when the part has to carry real load. Send the file through a review request and tell us which settings to test. A person reviews your request and follows up by email.
Sources
- Infill (Prusa Knowledge Base), Prusa Knowledge Base
States strength is mostly defined by the number of perimeters, not infill. Recommends 10 to 15 percent infill for most models, and states little sense in going above 40 percent.
- Materials 16(2):695, walls vs infill modulus study, Materials (MDPI, open access via PMC)
Young's modulus by infill percentage, 0 to 100 percent: 703, 877, 871, 995, 847, 1352 MPa, non-monotonic. By perimeter count, 1 to 3: 626, 720, 804 MPa. States increasing the wall perimeter count has much more effect per increment than infill density.
- Rogelj et al. 2025, PLA infill and perimeter tensile study, Polymers (MDPI, open access via PMC)
PLA tensile strength by infill percentage, 40, 60, 100 percent: 30.75, 32.94, 49.11 MPa. By perimeter count, 1, 2, 3: 21.79, 28.59, 32.94 MPa.
- Pattern vs density, ABS tensile study, PMC (peer-reviewed)
At 80 percent infill density, ABS tensile strength measured 17.46 MPa with a line pattern versus 38.95 MPa with a concentric pattern.
- Harpool et al. 2021, PLA infill pattern study, Materials (MDPI, open access via PMC)
PLA tensile strength measured 44.34 MPa at 100 percent solid infill versus 58.25 MPa at 15 percent hexagonal infill.
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Published 5 September 2026.