Print specifications are where POD sellers get contradictory advice: 300 DPI always, no — 150 is fine, convert to CMYK, no — never convert to CMYK. Most of it is half-remembered offset printing lore applied to digital print.
Here's what's true for print-on-demand specifically.
DPI is a relationship, not a property
The most useful thing to understand: an image file does not have a DPI in any meaningful sense. It has pixel dimensions. DPI is metadata describing how many of those pixels to lay down per inch when printing.
A 3000 × 3000 px file is:
- 300 DPI printed at 10 × 10 inches
- 150 DPI printed at 20 × 20 inches
- 600 DPI printed at 5 × 5 inches
Same file. Changing the DPI field in Photoshop without resampling changes nothing about the pixels — it just changes the label.
This is why "make sure it's 300 DPI" is incomplete advice. The question is always 300 DPI at what size?
The calculation
Pixels needed = print size in inches × target DPICommon POD sizes at 300 DPI:
| Product | Print size | Pixels needed |
|---|---|---|
| A4 poster | 8.3 × 11.7 in | 2480 × 3508 |
| A3 poster | 11.7 × 16.5 in | 3508 × 4961 |
| 18 × 24 in poster | 18 × 24 in | 5400 × 7200 |
| 24 × 36 in poster | 24 × 36 in | 7200 × 10800 |
| T-shirt front (DTG) | 12 × 16 in | 3600 × 4800 |
| 11oz mug wrap | 8.5 × 3.5 in | 2550 × 1050 |
| Tote bag | 12 × 14 in | 3600 × 4200 |
| 3 in sticker | 3 × 3 in | 900 × 900 |
Set your canvas to these dimensions at the start. Upscaling later never recovers detail that was never captured.
When 300 DPI is overkill
300 DPI is the standard because it exceeds what the eye resolves at reading distance — roughly 12 inches. Viewing distance scales:
| Print size | Typical viewing distance | Adequate DPI |
|---|---|---|
| Greeting card | 12 in | 300 |
| A4 / A3 print | 2–3 ft | 200–300 |
| 24 × 36 poster | 4–6 ft | 150–200 |
| Large canvas | 6–10 ft | 100–150 |
A 24 × 36 inch poster at 300 DPI is 7200 × 10800 px — a 200MB+ file that most POD uploaders reject. At 150 DPI it's 3600 × 5400, entirely acceptable at normal viewing distance, and it uploads.
However: check your supplier's minimum. Many specify 150 DPI minimum and reject below it regardless of your reasoning. Design to the supplier's spec, not to first principles.
AI-generated and upscaled artwork
Increasingly relevant, and worth being precise about.
Most image generators output at 1024 × 1024 or similar. That's 3.4 inches at 300 DPI — fine for a sticker, nowhere near enough for a poster.
Upscaling options, in order of quality:
- Generate at higher resolution natively where the model supports it. Always best.
- AI upscalers (Topaz Gigapixel, Real-ESRGAN, or the upscale built into most generation tools). These invent plausible detail and generally work well at 2–4×.
- Photoshop Preserve Details 2.0 (Image → Image Size → Resample: Preserve Details 2.0). Decent for 2×, soft beyond it.
- Plain bicubic upscaling. Adds pixels, adds no detail. Produces the soft, mushy prints that generate refund requests.
Order of operations matters as much as the tool: upscale the raw generation before you build the design around it, and only once. Midjourney for print-on-demand has the pixel maths per aspect ratio, including why the practical ceiling lands around A3 at 300 DPI.
Test honestly: upscale, then view at 100% zoom. That's approximately what the print will look like. If it looks soft on screen at 100%, it will look soft on paper.
The cleanest way to avoid the problem entirely is not to upscale later at all — master the artwork at the largest size you sell and let every smaller order downsize from it.
Which format to export as
Resolution and format are separate decisions, and getting the second one wrong undoes the first. Transparent uploads need PNG-24; full-bleed prints are fine as JPG at quality 95 or TIFF; PNG-8 should never touch a print file, because its 256-colour cap bands every gradient. Full mapping in PNG, JPG, WebP or TIFF for Etsy and print.
RGB vs CMYK: don't convert
The advice to convert to CMYK comes from commercial offset printing, where you're specifying ink plates directly.
Print-on-demand suppliers want RGB. Their printers use their own colour management to convert to whatever ink set the device uses, and their profile is better tuned than a generic Photoshop conversion. Converting to CMYK yourself throws away colour information and often produces duller results than leaving it alone.
Specifically:
- Submit sRGB. It's the safest, most universally handled profile.
- Adobe RGB is acceptable at some suppliers and produces slightly richer output where supported — check first.
- Never submit CMYK unless your supplier explicitly asks for it with a named profile.
Why prints look duller than your screen
This surprises every new seller, and it isn't a mistake you made.
Your monitor emits light. Paper reflects it. Screens can display colours — particularly vivid blues, bright greens and pure saturated oranges — that no ink on paper can reproduce. When those colours are printed, they map to the nearest achievable value, which is duller.
Mitigations:
- Avoid relying on the most saturated corners of the gamut. A design built from slightly desaturated colours prints closer to what you designed.
- Soft-proof in Photoshop: View → Proof Setup → Custom, select a coated paper profile, then View → Proof Colours. This simulates the print on screen. It's approximate, but it prevents nasty surprises.
- Calibrate your monitor if colour accuracy is central to your product. A basic colorimeter costs under $150.
- Order a sample. No amount of soft-proofing replaces holding the print.
Blacks are the other common surprise: pure black (0,0,0) prints as a slightly washed dark grey on many DTG garments and matte papers. Deep dark greys often look richer than pure black in practice.
Bleed, safe area and trim
For anything cut after printing — stickers, cards, posters that get trimmed:
- Bleed: extend the background 0.125 in (3mm) beyond the cut line. Without it, a slight cut misalignment produces a white sliver at the edge.
- Safe area: keep text and critical detail 0.125–0.25 in inside the cut line.
- Trim line: the intended cut. Cutting machines have tolerance of roughly ±0.0625 in.
Sticker-specific handling in the sticker mockup guide.
The mockup resolution question
Separate problem, opposite answer.
Mockups are for screens, so only pixel dimensions matter and DPI metadata is irrelevant. Etsy wants 2000px+ on the shortest side, displays up to 3000px, and anything larger just slows your listing page and your render times.
So: artwork at print resolution, mockups at screen resolution. The high-resolution artwork goes inside the Smart Object; the exported mockup comes out at 2000–3000px. Template specs in PSD file setup for mockups, and Etsy's display requirements in Etsy image size requirements.
If you're rendering a catalogue in bulk, this matters practically: templates built at 6000px take several times longer per render than 2500px ones and produce no visible improvement on a listing page.
Pre-upload check
Before a design goes to a supplier:
- Pixel dimensions ≥ print size × supplier's minimum DPI
- Viewed at 100% zoom, it's sharp — no upscaling mush
- Colour mode RGB, profile sRGB
- Transparent background is genuine alpha, saved as PNG, not a white rectangle
- Bleed present if the product is cut
- Critical detail inside the safe area
- Highly saturated colours soft-proofed, or accepted as approximate
- A sample ordered before the listing gets real traffic
Quick reference:
- Pixels = inches × DPI. Set the canvas correctly at the start.
- 300 DPI for anything held; 150 DPI is fine for large-format wall art (check supplier minimums)
- Submit RGB/sRGB. Never convert to CMYK yourself.
- Upscale with AI or Preserve Details 2.0, never plain bicubic
- Expect prints to be less saturated than your screen — soft-proof, then sample
- Artwork at print resolution; mockups at 2000–3000px
Frequently asked questions
What DPI do I need for printing?
300 DPI at the intended physical size is the conventional target for anything viewed at reading distance. DPI is not a property of a file, though — it is the relationship between pixel dimensions and printed size, so the same image can be sharp at A4 and unusable at A0.
Is 300 DPI always necessary?
No. Viewing distance scales with print size, so a large poster seen from across a room is fine at 150 DPI. Anything held in the hand — a card, a sticker, a mug wrap — genuinely needs the full 300.
How do I calculate pixels for a print size?
Multiply the physical dimension in inches by the DPI you want. A4 at 300 DPI is 8.27 by 11.69 inches, so 2480 by 3508 pixels. The print resolution checker does this for every common size at once, in your browser, and how to check the DPI of a PDF covers reading it out of a file someone has already sent you.
Should I convert my files to CMYK?
No. Supply sRGB and let the printer convert, because it knows its own press and inks. A file you have already converted gets converted again at the printer, and two conversions shift colour in ways you cannot predict.
Why do prints look duller than they did on screen?
Because a screen emits light and paper reflects it. Saturated blues, greens and neons in particular have no printable equivalent, and matte stock mutes further. Lift the darkest tones slightly before export and expect some loss at the top of the saturation range.