ABS shrinkage: how much it shrinks and how to compensate

ABS shrinks about 0.6 to 0.8% in typical FDM printing, and across brands and setups you'll see roughly a 0.4 to 0.8% range. That's the most contraction of the four common filaments. Some blogs cite higher numbers, but treat those as outliers. ABS is the material where shrinkage stops being an afterthought and starts driving how you set up the print.

One thing to get straight up front. The figure that matters to a maker is the dimensional error on the printed part, measured with calipers after it cools, not the "mould shrinkage" number a resin datasheet quotes. Different process, different number. And most FDM filament datasheets (Prusament, Polymaker) don't publish a shrinkage value anyway, so with ABS especially you want to measure your own prints rather than trust a spec sheet.

Why ABS shrinks (and warps) the most

Every thermoplastic contracts as it cools from print temperature to room temperature. The amount depends on the glass-transition temperature (Tg) and how far the plastic falls from the nozzle to ambient.

ABS is amorphous, so it doesn't crystallize, but it has a high Tg, around 105°C. That high Tg means a large print-to-ambient temperature drop, and a large drop means more contraction. That's why ABS lands at the top of the ranking below despite not crystallizing.

The same high Tg that drives shrinkage also makes ABS the worst warper of the group. Warping is separate from uniform shrinkage: it's the corner-lifting curl you get when parts of the print cool and contract at different rates, building internal stress. In practice this means an enclosure or heated chamber is effectively required for ABS of any size. Without one, big flat parts lift off the bed before you ever get to worry about final dimensions.

A few characteristics to keep in mind, all amplified on ABS because the numbers are bigger:

• Shrinkage is anisotropic. It's larger in X and Y than in Z, and holes and inner contours come out undersized more than the outer walls do. On ABS this gap is large enough that per-axis compensation earns its keep.
• It grows with part size. At 0.8%, that's 0.16 mm on a 20 mm feature but 1.6 mm across a 200 mm part. Long ABS spans need real compensation.
• Your thermal setup tunes it. An enclosure slows cooling and changes effective shrinkage, so a value calibrated with the lid on won't hold with it off.

How ABS compares to PLA, PETG, and ASA

Here's where the four common filaments land, most shrinkage to least. The ordering follows 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. ABS and its close cousin ASA behave almost identically on the shrinkage front, though ASA usually warps a little less.

How to compensate

With ABS, compensation is less optional than it is with PLA. The workflow:

1. Print a calibration object in the same thermal setup (enclosure on if that's how you'll print the real part). A 100 mm cube keeps the math easy.
2. Measure with calipers after it has fully cooled. Measure X, Y, and Z separately, because on ABS the axes really do differ.
3. Convert each measured shrinkage to a scale factor.

The formula:

scale% = 100 / (100 − shrink%)

A measured 0.8% shrinkage means scaling to 100 / (100 − 0.8) = 100.8%, or ×1.008, the top of the ABS window above.

Our material shrinkage calculator takes either a shrinkage percentage or your measured-vs-expected dimensions and returns the scale factor plus the slicer compensation value. Its ABS default is 0.8%, matching the top of the typical range here. Because ABS holes shrink noticeably more than outer walls, lean on the XY hole-compensation idea the calculator supports, and set per-axis compensation rather than one uniform number when you have a part with tight bores or press fits. This hole-versus-wall gap is the single most common reason an ABS part measures fine on the outside but won't accept a bearing or a screw.

Related reading

Switch material and both the numbers and the warp story change. Here are the siblings to this guide:

• PLA shrinkage
• PETG shrinkage
• ASA shrinkage

If you're chasing warp as much as size, our roundup of free 3D printing tools and calculators covers the flow, temperature, and calibration tools that go hand in hand with an enclosure.

Let GrandpaCAD size the part for you

Compensation is scaling, and per-axis scaling is fiddly to do by hand. 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 an ABS part comes off the bed at the size you actually asked for.

Sources and further reading

• PlastikCity: material shrinkage rates
• Bambu Lab forum: combatting hole shrinkage, with data
• 3DSourced: 3D print shrinkage for PLA, ABS, and PETG