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Print size and DPI calculator

The largest print a photo supports at gallery, standard or poster resolution, or the pixels a print size needs, with a warning when the ratio crops.

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Largest print at 300 PPI: 20 × 13.3 in50.8 × 33.9 cm
Pixels needed for the print size: 2,400 × 3,000 px7.2 MP

Standard print sizes at this resolution
Print	Effective PPI	Crop	Quality
4 × 6 in	1,000	None	300+ lab target
5 × 7 in	800	6.7%	300+ lab target
8 × 10 in	500	16.7%	300+ lab target
8 × 12 in	500	None	300+ lab target
11 × 14 in	364	15.2%	300+ lab target
12 × 18 in	333	None	300+ lab target
16 × 20 in	250	16.7%	240+ acceptable
20 × 30 in	200	None	150+ viewing distance
24 × 36 in	167	None	150+ viewing distance

A print is a grid of pixels spread over paper. Pixels per inch (PPI) is how many of them land in each inch, so the largest print is the pixel count divided by the PPI you are aiming for.

print size = pixels ÷ PPI
pixels needed = print size × PPI
fit PPI = min(long px ÷ long in, short px ÷ short in)
crop = 1 − (smaller ratio ÷ larger ratio)

The PPI targets are conventions, not rules: 300 is the figure photo labs usually quote, 240 is often still acceptable, and 150 can work for big prints seen from a distance. Ask your lab for its own guidance.
The size table fills each print edge to edge, so when the proportions differ the photo is cropped. The crop column is the share of the width or height trimmed (whichever is too long for the print), and the PPI is what is left after that trim.
Photos you load are read on this device and not uploaded. Orientation does not matter: a portrait photo is matched to the long side of each print.
Upscaling in software adds pixels but not detail; use it sparingly.

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Print size and DPI calculator

The method behind the numbers.