Image resolution for a t-shirt print
The Shirtready designer warns that an image will print blurry when it is below 150 dpi at the size you place it. Plan for at least 150 dpi at the printed size. For the full 36 × 50 cm print area, that is about 2,126 × 2,953 pixels.
How dpi works
Dpi is the pixel count divided by the printed size in inches. A 2,126 pixel wide image printed 14.2 inches wide is 150 dpi. The same file printed smaller has more dpi, and printed larger it has less.
The production plate is 300 dpi
Each order is built on a print plate of 5,315 × 6,496 pixels that covers 45 × 55 cm. That is 300 dpi. Your artwork is placed on that plate at the size you choose.
Vector files
SVG files skip the pixel check. The designer treats SVG as vector artwork, so it gives no dpi warning for them.
Size limits
A file can be up to 100 MB. The designer refuses an image with a side longer than 12,000 pixels, or more than 40 million pixels in total.