How to Size Designs for Shrink Plastic
Shrink plastic (often called Shrinky Dinks) reduces in size when heated, which means every design you draw, stamp, or print must start larger than the finished piece. This calculator tells you exactly how big to make your starting design so it ends up at the size you want.
Understanding the Shrink Ratio
Standard polystyrene (#6) sheets shrink to about 45% of their original dimensions. That means a 3-inch circle becomes roughly 1.35 inches after baking. Working backward, if you want a 1-inch charm you need to start at about 2.22 inches. The calculator handles this math for you instantly.
Maximizing Your Sheets
Shrink plastic sheets are not cheap, so fitting as many pieces as possible onto each sheet saves money. Enter your sheet dimensions above and the calculator will show how many pre-shrink pieces you can tile across the sheet with no overlap.
Pro Tip: Always bake a small test piece first. Different brands and even different batches can vary slightly in shrink ratio. Adjust the custom percentage in the calculator if your test piece comes out a different size than expected.
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Frequently Asked Questions
How much does shrink plastic shrink?▼
Standard polystyrene (#6) shrink plastic shrinks to roughly 45% of its original size in both width and height. That means you need to draw or print your design about 2.2 times larger than you want it to end up. The exact ratio varies slightly by brand, so always test a small piece first.
Does shrink plastic get thicker when it shrinks?▼
Yes. As shrink plastic reduces in width and height, it increases in thickness by approximately 3 times. A thin, flexible sheet becomes a rigid, much thicker piece after baking. This is normal and is what gives finished pieces their durability.
What temperature and time should I bake shrink plastic?▼
Most shrink plastic brands recommend baking at 325 to 350 degrees Fahrenheit for 2 to 3 minutes. The plastic will curl, twist, and then flatten out. Wait until it lies completely flat before removing it from the oven. Press it flat with a book or spatula immediately if needed.