How to Size Designs for Shrink Plastic
How much does shrink plastic shrink?
Shrink plastic shrinks to about 45% of its original size in both width and height, which means you need to draw or print your design roughly 2.2 times larger than you want it to end up. So a finished 1-inch charm starts at about 2.2 inches. A 3-inch starting piece becomes 1.35 inches after baking.
As the plastic loses width and height it gains thickness — the finished piece is about 3 times thicker than the original sheet, which is what gives baked shrink plastic its rigid, durable feel. The exact shrink ratio varies slightly by brand, so always test a small piece from a new batch before committing to a full sheet.
Shrink rates by brand
Most polystyrene (#6) shrink plastic is in the 40-50% range. Here are the published ratios for the brands most makers reach for:
| Brand | Shrinks to | Pre-shrink multiplier |
|---|---|---|
| Shrinky Dinks (original) | ~45% of original | 2.22x |
| Grafix Shrink Film | ~40-50% of original | 2.0x – 2.5x |
| Lucks Bake-Shrink | ~45% of original | 2.22x |
| Generic #6 polystyrene | ~40-50% of original | 2.0x – 2.5x |
| Inkjet shrink film | ~50% of original | 2.0x |
The calculator above defaults to a 45% shrink ratio. Use the custom percentage field if your test piece comes out a different size.
Why this calculator exists
Shrink plastic is unforgiving. Make a charm 10% too big and it’s now too big for a necklace setting. Make it 10% too small and the detail you drew is unreadable. The math is simple but easy to get wrong under deadline pressure. The calculator removes the chance to mess it up.
Maximizing your sheets
Shrink plastic sheets aren’t cheap, so fitting as many pieces as possible onto each sheet saves real money. Enter your sheet dimensions above and the calculator returns how many pre-shrink pieces tile across the sheet with no overlap. For irregular shapes, round up your bounding box and accept the wasted space — trying to nest organic shapes by eye usually costs more in time than it saves in plastic.
Baking tips for consistent results
- Bake at 325-350°F for 2-3 minutes. The plastic will curl and twist before flattening out.
- Wait until pieces lie completely flat before pulling them. If they cool curled, you can’t fix them.
- Press flat with a smooth book or spatula immediately after removing if you need extra flatness.
- Don’t overcrowd the tray — pieces can touch and fuse as they shrink.
Pro tip: Always bake a small test piece from a new batch first. Different brands and even different production runs of the same brand can vary by a few percentage points in shrink ratio. Adjust the custom percentage in the calculator if your test comes out a different size.
Selling your shrink plastic creations
Once you have a process dialed in, the math shifts from shrink ratio to profit margin. Use these to make sure your pricing covers materials, fees, and your time:
- Etsy Profit Calculator — reverse 2026 Etsy fees and get your listing price.
- Craft Show Calculator — if you sell at fairs, factor booth fees and travel into pricing.
- Sticker Cost Calculator — comparable cost math if you also make stickers from the same designs.
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.