Print Size Calculator

How to use the print size calculator

1. Fill in the fields — they start with a worked example.
2. Read the answer, and the arithmetic shown beneath it.
3. Copy the results, or adjust the inputs to compare scenarios.

About this tool

A digital image has no physical size. It has a pixel count, and it acquires a size only when you choose a resolution to print it at. That is the whole of this calculation: pixels divided by pixels-per-inch gives inches. A 6000 × 4000 photograph is twenty inches wide at 300 PPI and forty inches wide at 150 PPI, and it is the same file in both cases.

This is worth knowing before you order, because a print shop will happily accept a file that is too small and print it anyway. The result is not an error message but a soft, slightly mushy photograph that you paid for. Entering the pixel dimensions here first tells you which sizes the file can actually carry.

300 PPI is the print industry's habit rather than a law of physics. It comes from a 150 line-per-inch halftone screen at two samples per line, and it holds for anything read at arm's length. Viewing distance is the real variable: a billboard is often produced at 15 PPI and looks perfect from the road.

The verdict shown alongside the size reflects that. Rather than a pass or fail, it says what the resolution is good for, so a poster that will hang across a room is not rejected for failing a standard written for a magazine page.

Common uses

• Checking the largest sharp print a camera file can produce before ordering it.
• Deciding whether a photograph is good enough for a poster or only a postcard.
• Explaining to a client why their web-sized logo cannot go on a banner.

Frequently asked questions

How do I convert pixels to inches?

Divide the pixel dimension by the print resolution in pixels per inch. 3000 pixels at 300 PPI is 10 inches; the same 3000 pixels at 150 PPI is 20 inches.

Do I need 300 DPI to print a photograph?

Only for something held at reading distance, such as a book or a magazine. Posters are routinely printed at 150 PPI and large banners far lower, because they are seen from further away.

Can I make an image bigger without losing quality?

Not really. Upscaling invents pixels that were never captured, so it can smooth an image but cannot add detail that the sensor did not record.