Annealing Shrinkage Calculator

Enter your part's original size and filament material to calculate the annealed dimension, size loss, recommended anneal temperature, and the pre-scaled size to print so your part hits its target after annealing.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter Original Size (mm)
Input the intended dimension of your 3D printed part before annealing, in millimeters. This is your target size.
2
Select Material
Choose your 3D printing filament material from the dropdown list (e.g., PLA, PETG, Nylon). Each material has a characteristic shrinkage rate.
3
Review Your Results
The calculator will display the expected annealed size, the amount of size loss, the shrinkage rate, and the recommended pre-scaled print size.

Example Calculation

A product designer is creating a PLA prototype with a target dimension of 50 mm. To ensure accuracy after annealing, they need to calculate the expected shrinkage and the necessary pre-scaled print size.

Original Size (mm)

Material (select)

PLA

Results

49.00 mm

Tips

Material-Specific Shrinkage

Always use the correct shrinkage rate for your specific filament. Different brands and formulations of the same material (e.g., PLA vs. PLA+) can have slightly different thermal properties, leading to variations in shrinkage.

Pre-Scaling for Accuracy

For critical dimensions, pre-scaling your 3D model in your slicer software is essential. If your material shrinks by 2%, print the part 2% larger (e.g., 50 mm becomes 51 mm) to achieve the target size after annealing.

Annealing Temperature Control

Accurate control of the annealing temperature is crucial. Overheating can lead to excessive shrinkage or warping, while too low a temperature may not effectively relieve internal stresses, resulting in less dimensional stability than desired.

Managing Dimensional Accuracy with the Annealing Shrinkage Calculator

The Annealing Shrinkage Calculator is an indispensable tool for 3D printing enthusiasts, product designers, and manufacturing engineers who rely on post-processing techniques to enhance part properties. This calculator predicts the final annealed size, the precise amount of material loss, and recommends the pre-scaled print dimensions for various common filaments like PLA, PETG, and Nylon. For instance, a 50 mm PLA part, with a typical shrinkage rate of 2%, will become 49.00 mm after annealing, a critical detail for maintaining tight tolerances in 2025.

The Physics of Polymer Shrinkage During Annealing

Annealing is a heat treatment process that alters the microstructure of a material, typically to increase its ductility, reduce hardness, and relieve internal stresses. For 3D printed polymers, annealing causes a rearrangement of molecular chains, increasing the material's crystallinity and density. This densification results in a reduction of the part's overall dimensions, known as shrinkage. The extent of shrinkage is material-dependent and influenced by factors like annealing temperature, time, and cooling rate.

The calculation for annealed size is straightforward:

Annealed Size = Original Size × (1 - Shrinkage Rate / 100)

To achieve a target original size after annealing, the pre-scaled print size needs to be larger:

Pre-scaled Print Size = Original Size / (1 - Shrinkage Rate / 100)

Where Shrinkage Rate is expressed as a percentage.

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Compensating for PLA Shrinkage in a Prototype

A product designer needs to 3D print a 50 mm component using PLA filament. They plan to anneal the part to improve its strength and heat resistance. PLA typically has an annealing shrinkage rate of approximately 2%. The designer needs to know the final annealed size and the pre-scaled print size required.

Here's the calculation:

Original Size: 50 mm
Material (PLA) Shrinkage Rate: 2%

Step-by-step calculation:

Calculate Annealed Size: Annealed Size = 50 mm × (1 - 2 / 100) = 50 mm × 0.98 = 49.00 mm
Calculate Size Loss: Size Loss = 50 mm - 49.00 mm = 1.00 mm
Calculate Pre-scaled Print Size: Pre-scaled Print Size = 50 mm / (1 - 2 / 100) = 50 mm / 0.98 ≈ 51.02 mm

The 50 mm PLA part will shrink to 49.00 mm after annealing. To achieve the target 50 mm, the designer should print the part at 51.02 mm.

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Material Properties and Annealing Outcomes

Different 3D printing materials exhibit varying shrinkage rates and respond differently to annealing. PLA, for example, typically shrinks between 1.5% and 3%, gaining significant improvements in heat deflection temperature (HDT). PETG, known for its toughness, usually has a lower shrinkage rate, around 0.5% to 1%, with annealing primarily improving its mechanical strength and interlayer adhesion. Nylon, a high-performance polymer, can shrink between 1% and 2.5%, benefiting from enhanced stiffness and reduced moisture absorption. Polycarbonate, another engineering-grade material, generally shows minimal shrinkage (around 0.5%) but gains substantial impact resistance and high-temperature performance after proper annealing.

Expert Interpretation of Annealing Results

For material scientists and manufacturing engineers, interpreting annealing shrinkage goes beyond just the final dimension:

Dimensional Stability: Experts look for consistent and predictable shrinkage. A material with a lower, more consistent shrinkage rate (e.g., PETG at 0.7%) indicates higher inherent dimensional stability after thermal processing, making it easier to design parts with tight tolerances. Highly variable shrinkage suggests inconsistent material properties or annealing parameters.
Crystallinity Enhancement: Shrinkage is often correlated with an increase in crystallinity, which is a key goal of annealing polymers. Higher crystallinity generally leads to improved mechanical properties like tensile strength, stiffness, and heat resistance. For example, a PLA part that shrinks by 2.5% might have a significantly higher HDT than one that shrinks by only 1.5%.
Stress Relief Indicators: While shrinkage is a primary outcome, experts also observe for signs of warping or cracking during cooling. Minimal warping post-anneal, even with significant shrinkage, indicates effective stress relief. Conversely, uneven shrinkage or new deformations suggest that internal stresses were not uniformly dissipated.
Process Optimization: The shrinkage rate provides critical feedback for process optimization. If a part consistently shrinks more or less than expected, it prompts a review of the annealing temperature, soak time, or cooling rate to fine-tune the process for desired outcomes and ensure parts meet stringent quality control standards.

Frequently Asked Questions

What is annealing shrinkage in 3D printing?

Annealing shrinkage in 3D printing refers to the reduction in size that occurs when a printed part is heated to a specific temperature (below its melting point) and then slowly cooled. This process, typically applied to polymers like PLA or PETG, helps relieve internal stresses, improve crystallinity, and enhance mechanical properties, but it invariably causes the part to shrink, typically by 0.5% to 3% depending on the material.

Why do 3D printed parts shrink during annealing?

3D printed parts shrink during annealing primarily due to changes in their molecular structure and density. The printing process often leaves polymers in an amorphous, stressed state. Annealing allows polymer chains to rearrange, increasing crystallinity and density, which results in a more compact structure and a reduction in overall dimensions. This stress relief also improves dimensional stability.

Which 3D printing materials benefit most from annealing?

Materials like PLA, PETG, and Nylon typically benefit most from annealing. PLA, in particular, sees significant improvements in heat resistance and strength. PETG and Nylon also gain enhanced mechanical properties and reduced warping tendencies. Other materials like ABS and Polycarbonate can also be annealed, though their shrinkage rates and property changes vary.

How can I minimize or predict annealing shrinkage?

To minimize or predict annealing shrinkage, accurately measure your material's specific shrinkage rate through testing. Then, use this rate to pre-scale your 3D model in your slicer software, printing the part slightly larger than the target dimension. Controlling annealing temperature and cooling rates precisely also helps achieve consistent and predictable results.