Short answer
Print-on-demand platforms want enough pixels to cover the print area at 150 to 300 DPI. Printful asks for 150 DPI on apparel and 300 DPI on posters, mugs and phone cases. Printify recommends 300 DPI, or 120 to 150 DPI for large products. Redbubble lists a minimum pixel size for every product. The DPI tag alone changes nothing; the pixel count decides.
Key points
- Pixels needed = print size in inches × DPI. A 12 × 16 inch shirt print at 150 DPI is 1,800 × 2,400 px.
- Redbubble lists minimum pixels per product; 9,075 × 6,201 px covers its whole range.
- Typing 300 into the DPI box adds no pixels. Check the pixel size instead.
- Short on pixels? A 4× or 8× AI upscale to a transparent PNG usually closes the gap.
- Redraw thin text and logos as vector art; upscaling suits painted, photographic and textured art.
The short answer
Every print-on-demand (POD) platform asks the same question: does the file have enough pixels for the print area? Most want 150 to 300 DPI at the size the design prints. Printful calls 150 to 300 DPI ideal.
The math is one line. Multiply the print size in inches by the DPI, and you get the pixels you need.
Example: A T-shirt front printed at 12 × 16 inches (30.5 × 40.6 cm) and 150 DPI needs 12 × 150 = 1,800 px wide and 16 × 150 = 2,400 px tall.
Platforms often say DPI where they mean PPI, pixels per inch of the finished print. For a POD file the two mean the same thing.
Pixel sizes by platform
These are the numbers from each platform's own help pages. Checked: Oct 2026. Platforms change their rules, so check the product page in each design tool before you upload.
| Platform | DPI rule | Example sizes | Files and limits |
|---|---|---|---|
| Printful | 150 DPI for apparel, embroidery and all-over print; 300 DPI for posters, mugs and phone cases | T-shirt print area up to 12 × 16 in (1,800 × 2,400 px at 150 DPI); some DTG shirts 15 × 18 in (2,250 × 2,700 px) | PNG or JPG, sRGB, up to 200 MB |
| Printify | 300 DPI recommended; 120 to 150 DPI for large products such as leggings, blankets and tapestries | Shown per print area in the Product Creator | JPG or PNG up to 100 MB; SVG up to 20 MB |
| Redbubble | Pixel minimums per product; DPI does not affect the upload | Men's graphic T-shirt 3,873 × 4,814 px; other apparel 2,400 × 3,200; throw pillow 3,225 × 3,225; standard mug 2,700 × 1,120; phone case 1,187 × 1,852; art print 3,840 × 3,840; throw blanket 7,632 × 6,480 | JPG or PNG only; up to 300 MB or 13,500 × 13,500 px |
Redbubble also says one file of at least 9,075 × 6,201 px covers its entire product range. That is 56 megapixels, so most sellers make a few files in portrait, landscape and square instead.
Amazon's Merch on Demand is often quoted at 4,500 × 5,400 px for a standard shirt, a PNG at 15 × 18 inches and 300 DPI. Check the current requirement in your Merch account before you design to it.
Posters at 300 DPI
Printful asks for 300 DPI on posters. Here is what common sizes need:
| Poster | Pixels at 300 DPI | Pixels at 150 DPI |
|---|---|---|
| 8 × 10 in (20 × 25 cm) | 2,400 × 3,000 | 1,200 × 1,500 |
| 11 × 14 in (28 × 36 cm) | 3,300 × 4,200 | 1,650 × 2,100 |
| 16 × 20 in (41 × 51 cm) | 4,800 × 6,000 | 2,400 × 3,000 |
| 18 × 24 in (46 × 61 cm) | 5,400 × 7,200 | 2,700 × 3,600 |
| 24 × 36 in (61 × 91 cm) | 7,200 × 10,800 | 3,600 × 5,400 |
The 300 DPI in pixels guide has longer charts, and the fabric DPI calculator works out any size.
Why you see "low resolution"
A warning means the file spreads too few pixels over the print area. Printful gives the example of a file scaled up until it reaches 60 DPI, far below its 150 to 300 DPI range. The print then looks soft or blocky up close.
Some platforms let you publish anyway. Printify says it will enhance a low-resolution file before production, but it still recommends high-resolution designs that meet each product's rules. Fixing the file yourself means you see the result before a customer does.
Warning: Typing 300 into Photoshop's resolution box without resampling only changes a label. Redbubble's help page says DPI and PPI don't affect the uploaded image. Only more pixels make a bigger sharp print.
Check your file's real size
Open the file and read the pixel width and height, not the DPI. In Photoshop that is Image > Image Size; on a Mac, Preview's Tools > Adjust Size shows it too.
Then divide by the DPI the platform wants. A 1,500 × 1,800 px file at 150 DPI covers 10 × 12 inches. At 300 DPI it covers 5 × 6 inches. Our guide on how to check an image's DPI walks through more apps.
Short on pixels? Upscale
When the file is too small, an AI upscaler can enlarge it 4× or 8× and draw in new detail. A plain resize stretches the old pixels and looks soft, as the AI upscaling vs Photoshop resize guide shows.
Example: A 1,125 × 1,350 px design upscaled 4× becomes 4,500 × 5,400 px (24.3 MP). That covers a 15 × 18 inch shirt print at 300 DPI and Redbubble's 3,873 × 4,814 px men's T-shirt minimum.
Our Image Upscaler does 4× and 8× free, for results up to 36 megapixels. Transparent backgrounds stay transparent, and the download is a PNG tagged 300 DPI.
- Sign in to the Image Upscaler with a free account.
- Upload the largest copy of the design you have. JPG, PNG, WEBP, TIFF and PSD all work.
- Choose 4× or 8×, whichever first gets you past the pixels the product needs.
- Download the PNG and check edges, small text and fine lines at 100% zoom.
- Upload it to your POD platform and look at the product preview.
Free 8× works for designs up to about 750 × 750 px. For finer detail, or results up to 50 megapixels and a 16× option, Pro uses credits: 120 per upscale, or 180 above 36 MP. In the US, packs start at $1.49 for 250 credits. The 800% upscale guide explains how to pick the scale.
When to redraw instead
AI upscaling suits painted, photographic, textured and AI-generated art. It is the wrong fix for some files:
- A logo or wordmark. Redraw it as vector art, or ask the client for the original vector file.
- Small text. Retype it in your design app with a real font at full size.
- Flat, hard-edged shapes with only a few colors. Tracing them as vectors gives perfectly clean edges at any size.
You can mix both. Upscale the painted background, then add the text as a fresh layer on top.
Export checklist
- Pixels cover the print area at the platform's DPI.
- Color profile is sRGB, which Printful asks for.
- PNG when you need a transparent background. JPG does not keep transparency.
- File size is under the cap: 200 MB at Printful, 100 MB at Printify, 300 MB at Redbubble.
- No stray white box around the design. Turn off the background layer before you export.
- The product preview looks right at the size you chose.
Tip: Save one master file at the largest size you need and export smaller copies from it. Enlarging a small export again loses detail each time.
What to do next
Look up the pixel size your product needs in the table above or with the fabric DPI calculator. If your file falls short, upload it to the free Image Upscaler, choose 4× or 8×, and upload the transparent PNG to your shop.
Questions people ask
What size should an image be for print on demand?
Big enough to cover the product's print area at the platform's DPI. For a Printful T-shirt front that is up to 12 × 16 inches at 150 DPI, or 1,800 × 2,400 px. Each platform shows the exact size for each product in its design tool.
What is 4500 x 5400 pixels in inches?
At 300 DPI it is 15 × 18 inches (38.1 × 45.7 cm), because 4,500 ÷ 300 = 15 and 5,400 ÷ 300 = 18. At 150 DPI the same file covers 30 × 36 inches.
Does DPI matter for Printful or Printify?
Only as pixels per inch at the print size. Both platforms measure how many pixels land on each inch of the product. A 72 DPI file and a 300 DPI file with the same pixel size print the same.
Can I upscale a low resolution image for print on demand?
Yes, if the design is painted, photographic, textured or AI-generated art. An AI upscaler adds new detail, while a plain resize only stretches pixels. Thin text and logos look better redrawn as vector art.
Why does my print-on-demand site say my image is low resolution?
The file has too few pixels for the print area you chose, so each inch gets fewer pixels than the platform wants. Make the design smaller on the product, find a bigger original or upscale the file.