Notes
One master file for all four platforms
Preparing a separate file per platform multiplies the work and the mistakes. One master, scaled down at the last step, does not.
The master
| Canvas | 4500 × 5400 px |
|---|---|
| Resolution | 300 DPI |
| Physical size | 15″ × 18″ |
| Colour space | sRGB |
| Format | PNG |
| Background | transparent |
Why those numbers
4500 ÷ 300 = 15 and 5400 ÷ 300 = 18. That is the Merch by Amazon artwork size exactly — and Merch is the only one of the four with a genuinely mandatory dimension, so it sets the target. It also matches the 15 × 18 inch print area used by some Printful DTG products, and comfortably exceeds what Redbubble asks for on apparel.
The direction of travel matters
Products with a smaller print area are handled by scaling the master down at adaptation time. This only works in one direction. A master built too small cannot be recovered later, and enlarging it invents detail that was never captured — a file upscaled to pass a dimension check still prints soft, which is exactly the failure worth avoiding.
What each platform takes from it
- Merch by Amazon — the master unchanged. The dimensions are mandatory and this is them.
- Printful — the master unchanged for 15 × 18 DTG products; other products have their own print areas, listed on each product page.
- Redbubble — scaled down per product. The Graphic T-Shirt is 3873 × 4814, the Premium T-Shirt 2875 × 3900.
- Printify — scaled to whatever the chosen print provider states. There is no platform-wide size.
Frequently asked questions
Is one file really enough for everything?
One master is enough to derive everything. You still export per-platform files at the sizes each product states — but they all come from the same original, which means they are consistent with each other and none of them was ever enlarged.
What if a product needs something larger than the master?
Then the master is too small for your catalogue and should be rebuilt bigger. That is a decision to make once, at the start, rather than discovering it product by product.