Print size calculator: pixels to inches, cm and DPI

How print size is worked out

A printer does not care what a file says about itself. It cares how many pixels it has to spread over each inch of the product. That number is the DPI (dots per inch), and the sum is short:

Turned around: the largest sharp print of an image is its pixel size divided by 300. A 1024 × 1024 image, the size most AI models hand you, is sharp at 3.4 inches. That is a sticker, not a shirt.

Pixel to print size calculator: the sum by hand

To turn pixels into a print size, divide each side by the DPI you want. The answer is in inches; multiply it by 2.54 for centimeters.

The calculator above does this for both sides at once, at 300, 200 and 150 DPI, and checks the result against the print areas of real products. Choose “Print size to pixels” to go the other way, from inches or centimeters to the pixels you need. Pick a common size from the list or type your own, and rotate it for landscape.

Image DPI calculator: how to find an image’s real DPI

An image has no real DPI of its own until you decide how large to print it. Then it is one more division: the pixels on a side, divided by the inches that side will cover.

When the picture is a different shape from the print area, it is scaled until it fits inside, and one side is left with room to spare. The DPI shown under “On common products” already allows for that. To find the DPI at a size of your own, type one side under “Check a size of your own”; the other side follows the image’s shape.

Why changing 72 DPI to 300 DPI does nothing

Image files carry a DPI number in their details, and many guides say to set it to 300. That number is only a label. Changing it from 72 to 300 leaves every pixel as it was: the image has exactly as much detail as before, and it prints exactly as soft.

The only things that make a print sharper are more real pixels (make the image again at a larger size, or upscale it) or a smaller print.

How much is enough

• 300 DPI: the standard for anything held in the hand: stickers, mugs, phone cases, small chest prints.
• 200 DPI: good for shirts and hoodies. Fabric softens fine detail anyway.
• 150 DPI: the least most print-on-demand suppliers accept. Fine for posters and large prints seen from a step back.
• Under 150 DPI: edges turn soft and blocky. Make it bigger with the image upscaler, or print it smaller.

Print size chart in inches

The pixels a file needs for common photo, paper, poster and product sizes. Width comes first; turn both numbers around for a print in landscape. The 72 DPI column is the size the same page takes on a screen, too few pixels to print.

Print size chart in centimeters: A4, A3 and more

Paper and frames outside the United States are sold in centimeters. The sum is the same once the length is in inches: divide the centimeters by 2.54, then multiply by the DPI. At 300 DPI that is 118 pixels for every centimeter.

How big can I print my photo or AI image?

The same chart the other way round: the images people usually start with, and the largest sharp print each one makes.

Most AI images are made at about one megapixel: enough for a sticker, not a shirt. The image upscaler enlarges them two or four times; four times turns a 1024 × 1024 image into 4096 × 4096 pixels, sharp at 13.7 inches.

Very large files are worked out the same way. A 10000 × 3600 pixel panorama prints sharp at 33.3 × 12 inches, or as a banner of 66.7 × 24 inches at 150 DPI.

Numbers like 1200 or 2400 DPI belong to scanners and printers, not to files. A printer may place 2400 tiny dots of ink per inch, but it builds each pixel of your picture from many of them. For a print file, 300 DPI is as far as it is worth going; more pixels than that make the file larger without making the print look any sharper.

In the SlapMake studio a canvas can be started at the print size of the product, so what you design is already the right number of pixels.

Enough pixels make a print sharp, not bright. Whether its colors will survive the printer is a separate question, and the print color checker answers it.

Each line above assumes the picture is fitted inside the print area. To see which frame and poster sizes it fills edge to edge without cropping, use the aspect ratio calculator.

Read more on the blog

• Best DPI and Upscaling Settings for Midjourney and AI T-Shirt Prints
• How to design and print your own merch with SlapMake

Questions people ask