Infill Percentage Guide: What Does Your Part Really Need for Strength?

When someone says “make it stronger,” the first instinct is often to crank the infill all the way up. In most cases, though, that is both unnecessary and expensive. Infill percentage determines how much of the part’s interior is filled, and it directly affects the triangle of strength, weight, and cost. In this guide we clarify how much infill each type of job actually needs.

What Does Infill Actually Do?

The outside of a part — the walls and top/bottom surfaces — handles the visual appearance and most of the external strength. Infill supports this shell from the inside. Here is the interesting bit: beyond a certain point, increasing infill adds very little extra strength while noticeably increasing material and print time. That is why wall count is often more effective than infill percentage.

Around 15%: Decorative and Lightweight Parts

This is sufficient for display models, vases, shelf objects, and figurines that will carry no load. It prints fast, uses little material, and keeps the part light.

Around 25–30%: Everyday Functional Parts

A balanced choice for parts that see moderate loads — fixtures, box lids, light-duty handles. For most users this is the genuinely “strong enough” zone.

50% and Above: Load-Bearing and High-Stress Parts

Consider this for connector elements subject to impact or assembly parts exposed to shock. Approaching 100%, however, is rarely sensible — weight and print time increase dramatically while the gains diminish.

Factors Beyond Infill That Affect Strength

Do not evaluate the percentage alone — consider these factors as well:

• Wall (perimeter) count: often more effective than infill.
• Infill pattern: patterns such as gyroid or honeycomb provide strength in different directions.
• Material: PETG responds to impact more flexibly than PLA.
• Print orientation: layer adhesion is weak when layers run perpendicular to the applied load.

In short, knowing what your part will actually do in the real world gives far better results than blindly choosing 50%. If you want to be sure which ratio suits your part, tell us the intended use and reach out via our quick quote page — we will evaluate it together and select the right infill and wall settings.