Short answer
Infill is the lattice printed inside a part, between its outer walls. 20% suits most prints - it is our default. Go down to 10% for display pieces and figurines, up to 40–50% for parts bearing real loads or spanning large flat tops, and reserve 100% for the rare part that must be solid metal-replacement dense. Higher infill adds material and time, but far less than most people expect, because the shell stays the same.
What infill actually is
A printed part is not solid plastic by default. The slicer builds an outer shell - the walls, plus solid layers along the top and bottom - and fills the space between with a lattice pattern: crossing lines of plastic arranged in a grid. That lattice is the infill. You never see it unless the model has an opening or a window, and it exists for one reason: solid interiors are almost always a waste of plastic and time.
Infill density is simply what fraction of that interior space the lattice fills. Our upload page gives you a 10–100% slider, in steps of 10, with 20% preselected. The default is genuinely right for most of what people order.
The walls do the heavy lifting
The most useful thing to understand about infill: a part's stiffness and strength come mainly from its outer walls, not the interior. Bending or twisting a bracket loads its outer skin the way a loaded I-beam loads its flanges - the material in the middle barely participates. This is why a part with three walls and 20% infill outperforms one wall and 60% infill in nearly every real-world test, while printing faster and lighter.
So if a part ever snaps and your instinct is "more infill", check the wall count first - or check the orientation, since FDM parts separate between layers more easily than along them. Our design guidelines cover both. Raise infill for the specific jobs it is genuinely good at:
The slider, range by range
| Density | What it is for | Trade-off |
|---|---|---|
| 10% | Figurines, vases, decor, cosplay props, lamp shades | Lightest and cheapest; large flat tops may pit slightly |
| 20% · default | Organisers, phone stands, enclosures, brackets, most shop-style parts | The balance point - solid feel, modest time cost |
| 30–40% | Parts with big flat tops, drawers under load, tools with handles | Prevents pillowing; adds a little weight and time |
| 50% | Seriously loaded brackets, mounts, jig and fixture bodies | Noticeably heavier and slower - the practical working maximum |
| 100% | Parts that must be dense: weights, pestles, high-inertia mounts | Longest print times; can sink or warp on large sections; rarely needed |
What it does to weight and cost
Material cost follows weight (₹4 per gram for PLA and PETG), and infill is the main dial for weight. The key detail: the shell does not change. Walls, top layers, and bottom layers are printed identically at every density, so each step up in infill only fills more of the interior.
That is why doubling infill never doubles the price. Moving 20% → 50% adds a meaningful amount of plastic and machine time - on a palm-sized part it typically lands in tens of rupees, not double the order - while 10% → 20% is often nearly free. And unlike layer height, infill leaves the surface finish untouched; the two settings solve different problems.
How to choose in five seconds
Frequently asked questions
Is 100% infill the strongest option?
For a part crushed or pulled straight through its body, yes - solid plastic is the ceiling. But the jump from 50% to 100% is far smaller than from 20% to 50%, because the outer walls are already doing most of the work. Meanwhile 100% doubles or triples print time, adds noticeable weight, and can sink or warp on large flat areas. It is the right call for maybe one order in fifty.
What infill pattern do you use?
We match the pattern to the part when we slice: a grid-style lattice for general strength, denser support-oriented patterns under large flat tops. You choose the density with the slider; choosing the pattern is part of the slicing we handle.
Does infill affect the outer surface of the print?
Only at the top. Where a roof spans across the infill, too-sparse support underneath can show as small pits or sag - called pillowing - and that is the one cosmetic reason to raise infill (or add extra roof layers, which we handle when we slice). Walls and bottoms are unaffected at any setting.
Does infill change the shipping cost?
Indirectly, yes - a denser part weighs more, and shipping charges follow weight bands. The difference between 10% and 30% on a typical part is small, but on large solid-ish models it can tip the parcel into the next band. The quote you see already includes the final shipping estimate.
Infill or more walls - which should I choose for strength?
Walls, almost always. Going from three walls to five adds strength where bending loads actually act and barely affects print time, while the same strength from infill costs far more time and plastic. Raise infill when the part is loaded through its middle or has large flat tops - not as a substitute for thin walls.