In a print file, DPI (dots per inch) is the number of the image's pixels that land in each inch of the printed product, so it ties a file's pixel size to its physical print size: pixels = inches × DPI. Print providers usually ask for 300 DPI at the final print size, which means a design printed 12 inches wide needs to be 3,600 pixels wide.
This is for sellers who see "300 DPI" on every print checklist but are not sure what to change in their files, or who have had a "low resolution" warning on an upload. Once the relationship between pixels, inches and DPI is clear, you can tell a sharp file from a blurry one before it is printed, and you will not fall for fixes that change a number without adding any detail.
DPI and PPI: what each one counts
Two terms get mixed up, and it helps to separate them once.
PPI (pixels per inch) describes a digital image: how many of its pixels are spread across each inch when it is given a print size.
DPI (dots per inch) originally describes a printer: how many tiny dots of ink it places in each inch. A printer uses several dots to reproduce the colour of each pixel.
Print-on-demand file guides use "DPI" for both, and in practice they mean the pixel density of your file at the size it will be printed. This article follows that habit: when a provider asks for 300 DPI, they want 300 pixels for every inch of print.
The formula: pixels, inches and DPI
Everything comes from one equation, which you can turn around depending on what you know:
Pixels needed = print size in inches × DPI
Print size in inches = pixels ÷ DPI
Effective DPI = pixels ÷ print size in inches
So a design 3,600 pixels wide printed at 12 inches is 300 DPI. The same file stretched to 24 inches drops to 150 DPI. A 1,200-pixel image from a website, printed 12 inches wide, is only 100 DPI. This table gives the pixel widths for common print widths:
| Print width | Pixels needed at 150 DPI | Pixels needed at 300 DPI |
|---|---|---|
| 3 in (7.6 cm) | 450 | 900 |
| 4 in (10.2 cm) | 600 | 1,200 |
| 8 in (20.3 cm) | 1,200 | 2,400 |
| 10 in (25.4 cm) | 1,500 | 3,000 |
| 12 in (30.5 cm) | 1,800 | 3,600 |
| 15 in (38.1 cm) | 2,250 | 4,500 |
Work the same sum for height. A design 12 inches wide and 14 inches tall needs 3,600 × 4,200 pixels at 300 DPI.
Why 300 DPI is the usual target
Provider guidance centres on 300 DPI, with exceptions by product. One large provider says "The recommended resolution for JPEG/PNG files is 300 DPI" and asks for 120 to 150 DPI on large-format products. Another asks for files between 150 and 300 DPI, depending on the product, and elsewhere recommends at least 150 DPI for DTG products and 300 DPI for DTFlex products.
The reason is viewing distance. A shirt, a mug or an ornament is seen from close up, and at 300 pixels per inch the edges look smooth and fine lines and small lettering stay crisp. At lower densities, curves show stair-stepped edges and detail goes soft, and the printer reproduces that faithfully. Posters and canvases are usually seen from further away, which is why lower DPI is accepted for large-format work. If your design relies on fine detail, our note on thin lines and small text shows what holds up.
Changing the DPI number does not add detail
Image files store a DPI value in their metadata, and many web images are tagged at 72. Changing that tag to 300 without resampling does not make the file sharper: it only shrinks the size it prints at. A 1,200-pixel image relabelled as 300 DPI simply becomes a 4-inch print.
Resampling up, telling your editor to enlarge the image to more pixels, does reach the pixel count, but the new pixels are estimated from the old ones, so the result is bigger rather than more detailed. Better upscaling methods can rebuild edges convincingly on some images, and our guide to upscaling a low-resolution image for print covers when that works. Either way, judge a file by its pixel dimensions, never by the DPI field alone.
Size the file to the print area
DPI only means something at a specific print size. One major provider puts it plainly: "Make sure the file is sized to match the actual print dimensions to ensure DPI is calculated correctly."
Print areas differ between providers and products, so check the template for the product you are listing. One provider's standard front print area on select DTG tees moved from 12 x 16 inches to 15 x 18 inches, and other providers use other sizes. Our guide to t-shirt print areas covers front, back, sleeve and pocket placements. If your artwork is smaller than the area, that is fine: what matters is the pixel count across the part that will actually be printed.
DPI does not matter for your Etsy photos
Screens show pixels, not inches, so the DPI tag on a listing photo makes no difference. What Etsy asks for is pixel size: it recommends listing photos at least 2000 pixels in width and height, and a first photo at least 635 pixels wide and high so it does not show up lower in searches.
The simple rule: think in DPI at print size for the file you send the printer, and in pixels for the mockups you upload to Etsy.
How Alomations sets resolution for you
Alomations does this arithmetic for you: each design is delivered at 12 inches and 300 DPI, so 3,600 pixels on the long side, as a transparent PNG with an SVG beside it. The SVG is vector, so it has no fixed pixel count and can be rendered at any size without losing sharpness. Exporting the PNG yourself is covered in how to export a transparent PNG for a t-shirt design.
When a photo or an uploaded image is short of pixels, the Design Editor (paid plans) can enlarge it, and it can redraw flat art as vector so lettering and simple shapes stay clean at print size.
Frequently asked questions
Is 300 DPI always required?
No. It is the usual target for apparel, mugs and other products seen up close, but requirements vary by provider and product. One provider accepts 120 to 150 DPI for large-format products.
How many pixels do I need for a 12-inch print?
3,600 pixels at 300 DPI, or 1,800 pixels at 150 DPI. Multiply the inches by the DPI your provider asks for.
Does an SVG file have a DPI?
No. An SVG describes shapes rather than pixels, so it can be scaled to any size and is converted to dots only at printing. See what an SVG file is for when to use one.
Is a 72 DPI image too low for print?
Not necessarily. The tag alone tells you nothing. A 3,600-pixel-wide image tagged at 72 DPI still prints 12 inches wide at 300 DPI. Check the pixel dimensions.
Start on the Alomations free plan and every design you make comes back at 300 DPI, sized for print.