How Much Infill Do You Actually Need?
Quick Answer
10-15% for decorative items, 20-25% for general use, 40-60% for functional parts, 80-100% only for maximum strength
Most parts need far less infill than people expect: walls and shells do most of the work, and strength gains fall away above 50%.
Infill Percentage by Part Type
| Part type | Infill | Why |
|---|---|---|
| Decorative models, display pieces | 10-15% | Walls provide most of the stiffness; infill mainly braces the top surfaces |
| General-purpose parts | 20-25% | The common slicer default range; a good balance of strength, weight and time |
| Functional parts under load (tools, brackets) | 40-60% | Real strength for mechanical parts, at a clear material and time cost |
| Maximum strength or watertight parts | 80-100% | Heaviest and slowest option; rarely needed for anything else |
Material use does not scale one-to-one with the percentage: at 10-15% infill a typical part uses roughly 35-40% of the material of a solid print, at 20-25% roughly 45-55%, and only at 100% the full amount, because walls and top/bottom surfaces are always printed solid. The full density-by-band table is in our infill patterns reference.
Why Doubling Infill Does Not Double Strength
Strength increases with infill but with diminishing returns: going from 20% to 40% might increase strength by 30 to 50%, not 100%. The material cost, on the other hand, is linear. Using our infill calculator model, a 100 cm³ PLA part that would weigh 124g solid comes out at about 39.7g with 20% grid infill (68% material saved) and about 60.8g at 40% (51% saved). Doubling the infill adds roughly 21g of plastic for perhaps a third to a half more strength. If a part is failing, adding more perimeters is often more effective than raising infill.
Does the Pattern Matter?
Yes, sometimes more than the percentage. Gyroid and cubic give the best all-round, near-isotropic strength. Triangles are strong in one axis, and grid is fast but weaker diagonally. Lightning is the lightest pattern: it only braces the top surfaces and typically uses 50 to 70% less material than grid at the same nominal density, which makes it ideal for decorative parts and wrong for load-bearing ones. Patterns also lay down different amounts of material at the same slider setting: gyroid and cubic deposit a little more than grid (about 1.15 to 1.2 times), lightning far less (about 0.45 times).
When Is High Infill Worth It?
Reserve 80-100% for parts that must be watertight or take the highest loads; above 50% the strength returns are already diminishing. High infill also costs time: on a boxy part, going from 20% to 100% infill typically takes 2 to 3 times as long to print, because the printer deposits far more material inside the part. Our infill weight calculator shows the weight change per material, and the print time answer page shows what the same change does to the clock.