Material Shrinkage Scale Factor Calculator

All plastics shrink as they cool from the melt temperature to room temperature. For most FDM materials the shrinkage is small (0.2-0.5%) and within acceptable tolerances for general parts. For engineering applications and precision fits, it matters.

ABS and ASA are the worst of the everyday materials, at 0.5 to 0.8% linearly. A 100 mm ABS part comes out at 99.2 to 99.5 mm with no compensation, and over a 200 mm span that is a 1 to 1.6 mm shortfall. Nylon is worse again, and it carries a second problem on top: it absorbs moisture from the air and changes size again over the weeks after printing, so a nylon part measured on the day it came off the bed is not the part you have a month later.

Typical shrinkage rates (linear, room-temperature measurement):

• PLA: 0.2-0.3%
• PETG: 0.2-0.4%
• ABS: 0.5-0.8%
• ASA: 0.4-0.7%
• Nylon PA6: 0.8-1.5%
• Nylon PA12: 0.5-1.0%
• PC: 0.5-0.8%
• TPU: 0.5-1.0%

Scale factor formula:

scale (%) = 100 / (1 - shrinkage% ÷ 100) or equivalently: scaled_dimension = target / (1 - shrinkage%)

The dropdown uses the middle of each band above, so ABS is 0.65%: scale = 100 / 0.9935 = 100.654%, and a 100 mm target should be modelled at 100.65 mm. Pick your own number from the band with the custom field if you have measured a part. At the top of the ABS range, 0.8%, the same target wants 100.81 mm, and that 0.16 mm gap between the two ends of one material’s band is why measuring beats looking it up.

Important caveat. Shrinkage in FDM is not perfectly isotropic. X and Y directions (within the print plane) typically shrink more than Z (layer stacking direction). If precision is critical in all three axes, measure and compensate each axis separately.

Measure, then come back. These figures get you close on the first print. What actually settles it is printing a 100 mm test bar, measuring it cold with callipers, and putting the shortfall into the custom field. Our dimensional compensation calculator works the same problem from the other end, starting with a target and a measured dimension. The two agree: a 100 mm target measuring 99.35 mm gives 100.654% there and 100.654% here.

One thing that trips people up. Shrinkage compensation and horizontal expansion are not the same setting and do not stack cleanly. Scale corrects an error that grows with the dimension. Horizontal expansion corrects a fixed per-wall offset that is the same on a 10 mm part and a 200 mm one. If your 20 mm holes and your 200 mm outline are both wrong by the same absolute amount, it is not shrinkage.