How to Prepare Print-Ready T-shirt Design Files (DPI, Size, PNG and Colours)

Most bad prints are not printer problems. They are file problems: a small image stretched too large, a white box around the design, or soft shadows that turn into a grey haze on a black tee. This guide gives you the settings we use on our own print floor, so what you see on screen is what your customer receives.

The five rules of a print-ready file

Merch Factory accepts high-resolution transparent PNG files and checks the resolution when you place the design, so you know before ordering if a file is too small. Full specs are in our design guidelines tool.

Step 1: Work out the size in pixels

Printers work in inches, screens in pixels. The link is DPI (dots per inch): pixels = inches × DPI.

Not sure about your file? The DPI to pixel converter does the maths for you.

Step 2: Start big, never upscale

Create the canvas at full size from the beginning. Online “increase DPI” tools only change a number in the file; they cannot add detail that is not there. If you only have a small image, redraw or vectorise it, or use a proper AI upscaler and check every edge at 100% zoom.

Step 3: Remove the background properly

A white or checkered background that is not truly transparent will print as a rectangle. Delete the background layer and check by placing a coloured layer behind the design. Watch for leftover white pixels around hair, text and outlines.

Step 4: Design for the fabric colour

Dark T-shirts

DTF prints a white layer under your colours. Any pixel that is partly transparent (soft drop shadows, glows, faded brush strokes) still gets that white base and shows as a hazy halo. Use solid edges, or turn soft effects into halftone dots that are either fully on or fully off.

Light T-shirts

Very light colours such as pale yellow or light grey can almost disappear on a white tee. Add an outline or pick stronger colours.

Thin lines and small text

Keep lines at least about 1 mm thick and text at least about 8 pt at print size, so they hold up after washing.

Step 5: Export from your app

• Photoshop: hide the background, File → Export → Export As → PNG, transparency on, size at 100%.
• Illustrator: File → Export → Export As → PNG, resolution 300 ppi, background transparent.
• Canva: Download → PNG, tick “Transparent background” (needs a paid plan), and use the largest size option.
• Procreate: hide the background colour layer, Share → PNG; create the canvas at print size and 300 DPI from the start.

Final checklist before you upload

1. Transparent PNG, not JPG.
2. 300 DPI at the size it will print.
3. No white box, no stray pixels.
4. No soft shadows or glows on dark garments.
5. Lines and text thick enough to survive washing.
6. You own the rights to every element (see our copyright guide).

Want to understand the printing itself? Read DTF vs DTG printing and the DTF glossary entry.