Print size & DPI calculator

How to use the print size calculator

Choose Photo → print size to see how large an image can be printed, or Print size → pixels to find the resolution a print needs.

1. Enter the photo’s width and height in pixels, choose the photo itself (it never leaves your device), or pick a common camera size. To look the size up yourself, swipe up on the photo or tap its info button on a phone, open Properties → Details on Windows, or use Tools → Show Inspector in Mac Preview.
2. Pick a quality level. 300 PPI is the usual target for photos viewed up close, and 150 PPI is a practical minimum for posters.
3. Read the maximum print size, then check the common print sizes table for the quality and cropping you’d get at each size.

The pixels-to-inches math is simple: print size in inches = pixels ÷ PPI, and pixels needed = inches × PPI. Multiply inches by 2.54 for centimeters. A 4032 × 3024 photo at 300 PPI prints at 13.4 × 10.1 in (34.1 × 25.6 cm).

DPI vs PPI: what’s the difference?

PPI (pixels per inch) describes your image: how many of its pixels are spread across each inch of paper. It’s the number this calculator works with, and it’s what print shops usually mean when they ask for a “300 DPI” photo.

DPI (dots per inch) describes the printer: how many tiny dots of ink or toner it can place in an inch. Printers build thousands of shades from a few inks by printing patterns of dots (halftoning or dithering), so each image pixel is usually printed as several dots. That’s why a printer rated at 4800 × 1200 dpi doesn’t need a 4800 PPI photo. Those two numbers describe how finely it places dots across and down the page, not the image resolution you need to supply.

The DPI value saved inside an image file, often 72 or 300, doesn’t change its pixels either. It only sets a default print size, so the pixel dimensions are what count.

What PPI should you print at?

300 PPI is the long-standing target for photos you hold in your hand. Epson, for example, recommends an image resolution of 300–360 pixels per inch and notes that the right level depends on viewing conditions. Bigger prints are usually seen from farther away, where fewer pixels per inch look just as sharp. A common rule of thumb, based on 20/20 vision resolving about one arcminute of detail, is PPI needed ≈ 3438 ÷ viewing distance in inches. People also tend to view a print from about 1 to 1.5 times its diagonal.

Treat these as minimums: sharper eyes, close inspection and fine detail such as small text all benefit from more. That’s why the calculator’s ratings assume close viewing: Excellent at 300+ PPI, Very good at 240–299, Good at 200–239, Fair at 150–199 and Poor below 150.

Aspect ratio and cropping

Most DSLR and mirrorless cameras take 3:2 photos, while most phones take 4:3. Print sizes have shapes of their own, so when a photo fills the paper edge to edge, whatever doesn’t fit is trimmed. 4 × 6, 12 × 18, 20 × 30 and 24 × 36 match 3:2 exactly, but 8 × 10 and 16 × 20 are 4:5, which is why an 8 × 10 cuts so much from a camera photo.

To control what’s cut, crop the photo to the print’s shape yourself before printing. To keep the whole picture, choose the print dialog’s option to fit the entire image (Print Entire Image in Mac Preview, for example) instead of filling the page, and you’ll get white borders rather than a crop. The calculator’s common print sizes table gives the exact figure for your photo.

Megapixels to print size: how big can you print?

Print width grows with the square root of the pixel count, so doubling megapixels doesn’t double the print: a 48 MP photo prints only about twice as wide as a 12 MP one. Here are the largest sizes for common resolutions, using the whole photo.

The last column is the biggest size from the calculator’s list that still gets 300 PPI when the photo fills the paper. For exact paper dimensions in inches and millimeters, see the paper size chart.

Tips for sharp photo prints

• Start with the original file. Photos sent through messaging apps or saved from social media are often resized and compressed, so ask for the original.
• Don’t count on upscaling. Enlarging an image in software adds pixels, not real detail. It can hit a PPI number, but a small photo will still look soft on a big print.
• Print at 100% scale. If you’ve already sized the image for the paper, choose Actual size or 100% so the driver doesn’t resize it, and check the fit or fill setting whenever the photo’s shape differs from the paper.
• Watch borderless settings. Borderless printing enlarges the image slightly so it runs past the paper’s edges, trimming a thin strip on every side. Keep important details away from the edges.
• Check the printer first. Print a printer test page to spot banding or missing colors, and follow our print quality guide if something looks off.