Why is my slicer's weight higher than this calculator?

Because perimeter walls, top and bottom solid layers are not included here — they can add several grams.

What infill percentage should I use?

10–20% for decorative parts; 40%+ for functional or load-bearing prints.

Infill Weight Calculator — 3D Print Infill Grams

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Enter your values to see the infill weight estimate

Infill is the internal structure of a 3D print — the lattice, grid, gyroid or honeycomb pattern that fills the space between the outer walls and the solid top/bottom layers. Understanding how infill percentage affects weight lets you make smarter decisions: choosing the minimum effective infill for the application saves material and time, while over-inflating infill wastes both without meaningful strength gains for many geometries.

The formula, explained step by step

Infill weight ≈ model volume (cm³) × (infill% ÷ 100) × material density (g/cm³)

This formula calculates the mass of the infill structure only. It treats infill as a solid block scaled to the infill percentage — which is a good approximation for most practical calculations.

Step 1 — Model volume:
The model volume is the total enclosed space of the 3D model, as if it were solid. A 20 cm³ model has the same volume as a 20 ml container of water. This is provided by your slicer (object info panel) or CAD software.

Step 2 — Infill fraction:
Multiply by infill ÷ 100. A 20% infill means 20% of the internal volume is filled with material: 20 × (20 ÷ 100) = 4 cm³ of effective solid material from infill.

Step 3 — Apply material density:
4 cm³ × 1.24 g/cm³ (PLA) = 4.96 g of infill material

Important limitation: This gives the infill weight only. The actual print weight is higher because of: outer perimeter walls (shell/perimeters), inner walls (if using more than 2 perimeters), and solid top and bottom layers. These can add anywhere from 20% to 200% more material, depending on the model's surface-to-volume ratio. A thin-walled tall vase is almost entirely wall material with minimal infill; a large solid block is mostly infill.

How to use this calculator

Find the model volume in cm³. There are several ways: (a) Most slicers show object volume — in PrusaSlicer right-click the model and look at object info. In OrcaSlicer/Bambu Studio, the object properties shows volume in mm³ (divide by 1000 to get cm³). In Cura, enable "Volume" in the model info plugin. (b) Most CAD software (Fusion 360, FreeCAD, SolidWorks) shows volume in the mass properties or object properties panel. (c) Use an STL volume calculator tool (several free web-based tools accept STL files and report volume in cm³).
Enter your infill percentage. Use the same infill % you plan to set in your slicer. Common values: 10–20% for display parts, 20–40% for general use, 40%+ for functional parts.
Set the material density. PLA: 1.24 g/cm³. PETG: 1.27. ABS: 1.04. TPU: 1.21. Nylon: 1.14. See the full table below.
Interpret the result. The infill weight is just one component of total print weight. The "if 100% solid" figure tells you the maximum possible weight — no real print exceeds this. Your actual slicer-estimated weight will be somewhere between the infill-only estimate and the 100% solid estimate, depending on wall count and top/bottom layer thickness.

Understanding the relationship between infill, walls, and weight

A common misconception: "20% infill means the print is 20% as heavy as a solid print." This is rarely true, because walls and solid surfaces are a major fraction of the total material.

Consider a hollow cube, 40mm on each side, 2 perimeter walls, 4 top/bottom layers, 0.4 mm nozzle, 0.2 mm layer height:

Wall material (2 perimeters × 6 faces × ~0.8 mm wall × 40 mm² area) ≈ 7.7 g
Top + bottom layers (4 × 0.2 mm × 40 × 40 mm area × 2 faces) ≈ 3.2 g
Infill at 15% of internal volume (36 × 36 × 36 mm = 46,656 mm³ = 46.7 cm³) ≈ 8.7 g
Total ≈ 19.6 g

The infill is 44% of the total weight, not 15%. For this geometry, at 15% infill, the print is about 40% as heavy as it would be at 100% solid (49.4 g calculated solid). The infill contribution depends enormously on geometry.

Infill percentage guidelines by use case

5–10% infill: Decorative objects where internal structure only serves to prevent surface collapse. Vases, lamp shades, light figurines. The internal gyroid or honeycomb gives the surface layers something to rest on. Below 5%, surfaces can visually sag between layers.

10–20% infill: General-purpose display items, toys, cosplay props that won't see significant mechanical stress. Most hobbyist printing falls in this range. Gyroid and cubic patterns at 15% provide good surface quality with minimal material use.

20–40% infill: Everyday functional parts that see light to moderate loading: cable holders, mounting brackets, organizers, prototypes. This range offers a good strength-to-material tradeoff for most applications.

40–60% infill: Structural parts under regular stress: gear components, mechanical linkages, structural brackets, bike mounts. The stiffness increase from 40% to 60% is significant for many geometries.

60–80% infill: High-load structural parts where material is not a concern. Impact-resistant cases, sports equipment parts, load-bearing fixtures. At this range, the infill pattern (cubic, gyroid, honeycomb) matters significantly for isotropy.

80–100% infill: When maximum material density is needed regardless of weight. Rarely used in hobby printing. If you need near-solid parts, consider adjusting wall count instead of pushing infill — 5 or 6 perimeters often gives better strength than 50% infill with 2 perimeters, at similar or lower material cost.

Infill patterns and their effect on strength vs. weight

Grid / Rectilinear: Fast to print, good compression strength along vertical axis. Weak in diagonal directions. Default for many applications.

Gyroid: Equal strength in all directions (isotropic). Slightly heavier than grid at the same % due to more material overlap at intersections. Best for functional parts that see loads from multiple directions. Favorite of many experienced makers.

Honeycomb: Strong under compressive vertical load, good in-plane stiffness. Slightly slower to print than grid. Good for flat structural panels.

Cubic / 3D Honeycomb: Excellent isotropic strength. Print time similar to gyroid. Good for impact resistance.

Lines / Zig-zag: Fastest to print, weakest structurally. Use for supports or very low-demand applications only.

Real-world examples

Example 1: Mechanical arm bracket

Volume: 35 cm³, PETG at 1.27 g/cm³. At 25% infill: 35 × 0.25 × 1.27 = 11.1 g infill. Estimated total print weight (slicer): ~18 g (walls and solid surfaces add ~7 g). At 50% infill: 22.2 g infill, total ~28 g — 56% more material for a significant strength increase under the arm's expected bending loads.

Example 2: Display figurine with complex geometry

Volume: 45 cm³, PLA at 1.24 g/cm³. At 10% infill: 45 × 0.10 × 1.24 = 5.6 g infill. The figurine has a large surface area relative to volume (fine details, thin limbs), so wall material dominates: estimated total ≈ 22 g. Increasing to 25% infill: 14 g infill, total ≈ 30 g. The 15% additional infill adds 36% more material for no visible or functional benefit on a display figurine — 10% is correct here.

Example 3: Impact-resistant phone case

Volume: 28 cm³, TPU (flexible, 95A) at 1.21 g/cm³. At 40% infill: 28 × 0.40 × 1.21 = 13.6 g infill. The flex of TPU means high infill makes the case stiffer and less effective at absorbing impact. For TPU cases, 15–25% gyroid or honeycomb provides better impact absorption than 40%+ grid infill, at lower material cost. At 20% infill: 6.8 g — half the material with better functional performance.

Common mistakes with infill settings

Using high infill as a substitute for proper wall count. For most strength requirements, adding perimeters (3 → 5 walls) is more effective and material-efficient than increasing infill from 20% to 60%. The walls carry most structural loads; infill primarily prevents the surface from collapsing. Adding 2 extra perimeters costs less material than doubling infill, with better load-bearing performance for most real-world loads.

Not accounting for wall material in total weight estimates. The infill-only calculation from this calculator must be used alongside knowledge of your wall count and layer thicknesses to estimate total print weight. For a quick total estimate, slice the model with your settings and read the slicer's gram estimate directly.

Assuming infill percentage changes proportionally with strength. Going from 20% to 40% infill doesn't double strength. The relationship is non-linear and geometry-dependent. Beyond a certain threshold (around 40–60% for most patterns), additional infill yields diminishing strength returns at linear material cost.

Recommended: For structural or engineering parts, PETG offers better layer adhesion and impact resistance than PLA at similar cost. Carbon-fiber reinforced PETG-CF or PA-CF takes it further for high-load applications.

Frequently asked questions

Why is my slicer's total weight higher than this calculator's result?

This calculator estimates the infill portion only. The complete print weight includes: outer perimeter walls (2–5 shells add significant material), inner perimeters (for multiple wall counts), solid bottom layers (typically 3–5 layers of 0.2 mm thickness), and solid top layers. For a typical desktop print with 3 walls and 4 top/bottom layers, walls and solid surfaces can represent 50–80% of total material weight — sometimes more than the infill. Use the slicer's own gram estimate for total weight; use this calculator to understand the infill component.

How do I find the model volume?

Multiple methods: (1) PrusaSlicer: right-click the model → "Object info" shows volume in mm³ — divide by 1000 for cm³. (2) OrcaSlicer/Bambu Studio: select the model, check the info panel for volume. (3) Cura: use the "Model info" or similar plugin. (4) Fusion 360, FreeCAD, SolidWorks: open the model's mass properties — volume is shown in the units of your workspace. (5) Web STL analyzer tools: upload your STL file for instant volume in cm³. If you can't find it, run a quick test slice and check the slicer's estimated filament consumption — scale from there.

What infill percentage is best for strength?

For general functional parts, 20–40% with a good pattern (gyroid, cubic) is optimal — adding more infill yields diminishing returns. For maximum strength per gram of material, increase wall count (perimeters) rather than infill: 5 perimeter walls with 20% gyroid infill is often stronger than 2 walls with 60% rectilinear infill, especially under bending loads. True maximum strength requires 100% infill plus maximum walls — rarely needed and very slow to print. Identify the actual load your part faces before defaulting to high infill.

Does infill pattern significantly affect weight?

At the same percentage setting, the weight difference between most infill patterns is under 5%. Grid and rectilinear are usually the lightest; gyroid and cubic slightly heavier due to the way they fill space at intersections. The weight difference at 20% between grid and gyroid is typically 1–3%. For practical purposes, choose your pattern based on strength characteristics, not weight — the difference is negligible.

Does infill affect print time as much as it affects weight?

Yes — approximately proportionally. Doubling infill from 20% to 40% roughly adds the same fraction of print time as it does material weight. For a part where infill represents 40% of total print time, going from 15% to 30% infill adds about 20% to the total print time. Complex patterns (gyroid, honeycomb) print slightly slower than simple patterns (grid, lines) at the same percentage due to more direction changes. For time-sensitive production, grid infill at the minimum needed percentage is the fastest option.

What's the lightest useful infill for a functional part?

For a purely structural part that needs to resist compression or bending: 15–20% with gyroid or cubic is often sufficient for light-duty applications. Below 10%, surface quality suffers (the top layers have too little support and can visibly sag). For display or decorative objects: 8–12% is fine. For resin prints: infill percentage works differently — typical hollow-print settings use drain holes and a wall thickness rather than a percentage, since resin infill doesn't work the same way as FDM.

Can I use this calculator for resin prints?

With significant caveats. Resin printers don't use infill the same way FDM printers do. Many resin prints are sliced as hollow shells with drain holes — the "infill" is the enclosed liquid resin that is later removed through drain holes. If you're printing a solid resin model (no hollow), the formula works the same way. Use your resin's density (most standard photopolymer resins cure to 1.1–1.2 g/cm³) and enter 100% infill for solid prints. For hollow resin prints, the calculation doesn't apply directly.

How does infill affect the strength of flexible materials like TPU?

For flexible filaments (TPU, TPE), infill percentage affects stiffness more than strength. Higher infill = stiffer, less compressible. Lower infill = softer, more flexible, better shock absorption. For phone cases, protective bumpers or flexible grips, 15–25% gyroid or honeycomb gives the best combination of flexibility and surface support. For rigid structural parts in TPU (minimal flex needed), 40%+ adds stiffness. This is why "flexible filament at 100% infill" produces a surprisingly rigid part — the material itself is flexible, but a solid block of it is quite stiff.

Should I use higher infill or more walls for a stronger part?

More walls (perimeters) are almost always more effective for load-bearing parts than higher infill. Walls bear loads directly; infill transfers loads between walls but contributes less to the structural capacity per gram of material. As a practical guideline: for bending resistance, 4–5 perimeters at 20% infill outperforms 2 perimeters at 60% infill, using similar material. For compression resistance (parts being squeezed), infill matters more. Try both settings in your slicer and compare the gram estimates — then choose the lighter option that meets your strength requirements.

Infill Weight Calculator