How large an image do I need to print a 32″ by 18″ poster at 300 DPI?

Question

I need to have an image printed as a poster at 300 DPI, but am unsure of how big the file must be. Also, what file format is best?

Asked by Jake223

Answer

The straightforward answer to your question is very simple arithmetic: 32×300 = 9600 and 18×300 = 5400, so 32 inches by 18 inches at 300 dots per inch is 9600 by 5400.

However, it gets a little more complicated when you consider a more complicated relationship between pixels and colored dots in your output medium. For details on this, take a look at jrista's answer to a similar question: What DPI should I resize my image to for best printing quality?, at What does DPI mean?, and at Is there a general formula for image size vs. print size?

It sounds like you're doing something specific, though. In that case, the best answer is to ask your print service what they recommend — and the same thing goes for file format (and color space, a whole 'nuther can of worms).

Answered by mattdm

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