PETG shrinkage: how much it shrinks and how to compensate

PETG shrinks about 0.4 to 0.6% in typical FDM printing, with most setups landing somewhere in the 0.2 to 0.6% range. That puts it between PLA and the ABS family: a little more movement than PLA, comfortably less than ABS. It's low and predictable enough that PETG is a solid pick for functional parts where tolerances matter.

First, a distinction that saves a lot of confusion. What we're measuring here is the dimensional error on a real printed part, checked with calipers once it cools, not the "mould shrinkage" figure a resin datasheet quotes. Those are different numbers for different processes. And most FDM filament datasheets (Prusament, Polymaker among them) don't publish a shrinkage value at all, so the reliable approach is to measure your own prints.

Why PETG stays dimensionally stable

Thermoplastics contract as they cool from the nozzle back down to room temperature. How much they contract comes down to the glass-transition temperature (Tg) and the size of the print-to-ambient temperature drop.

PETG is glycol-modified PET, an amorphous polymer with a moderate Tg around 80°C. Amorphous means it doesn't crystallize on cooling, so there's no extra volume collapse from crystal packing, and the moderate Tg keeps the temperature drop manageable. The result is shrinkage that's low, uniform, and repeatable, which is exactly what you want when a part has to fit something else.

A few characteristics that hold for PETG like any FDM material:

• Shrinkage is anisotropic. It's typically larger in X and Y than in Z, and holes and inner contours come out undersized more than the outer walls.
• It scales with part size. At 0.5%, that's 0.1 mm on a 20 mm feature but 1 mm across a 200 mm part. Small parts often need nothing; long ones might.
• Warping is a separate failure. Warp is corner curl from uneven cooling, not a uniform size change. PETG warps modestly, less than ABS, more than PLA.

How PETG compares to PLA, ABS, and ASA

Here's where the four common filaments sit, most shrinkage to least. The ordering is driven by glass-transition temperature and the print-to-ambient drop, not crystallinity, since all four print effectively amorphous.

ABS and ASA sit at the top together, PETG in the middle, PLA at the bottom. PETG's spot in the middle is a big reason it's popular for brackets, enclosures, and mechanical parts: enough temperature resistance to be useful, without ABS's shrink and warp headaches.

How to compensate

If the fit matters, the workflow is the same for every material:

1. Print a calibration object. A 100 mm cube keeps the math simple, or use a part with the dimension you actually care about.
2. Measure with calipers after it has fully cooled. Average the X and Y sides.
3. Work out your shrinkage percentage, then convert it to a scale factor.

The formula:

scale% = 100 / (100 − shrink%)

A measured 0.5% shrinkage means scaling to 100 / (100 − 0.5) = 100.5%, or ×1.005, right in the middle of the PETG window above.

Our material shrinkage calculator does this both ways: enter a shrinkage percentage, or enter your measured and expected sizes and it derives the percentage for you, then gives you the scale factor plus the slicer compensation value. Its PETG default is 0.4%, at the low end of the typical range here. The calculator also covers the XY hole-compensation concept, which matters for PETG specifically because it's so often used for press fits and threaded inserts, where the hole shrinking more than the wall is what breaks the fit.

For a purely cosmetic PETG print, you can usually skip compensation. For anything that mates with hardware or another printed part, calibrate once and save the value in the filament profile.

Related reading

The numbers and the warping story shift as you change material. Here are the siblings to this guide:

• PLA shrinkage
• ABS shrinkage
• ASA shrinkage

Setting up a new machine? Our roundup of free 3D printing tools and calculators covers flow rate, E-steps, and the rest of the calibration you'll want alongside shrinkage.

Let GrandpaCAD size the part for you

Compensation is just scaling, and that's easy to hand off. Describe the part in plain English, tell GrandpaCAD the material and the fit you need, and it can model the geometry pre-scaled to compensate, so what comes off the bed measures the way you intended.

Sources and further reading

• 3DSourced: 3D print shrinkage for PLA, ABS, and PETG
• PlastikCity: material shrinkage rates