Files & prepress
What is effective dpi?
Also called: Effective resolution
Effective DPI is an image's real resolution at the size it will actually print — its pixel dimensions divided by the final print dimensions — and it's the only resolution number that predicts print quality.
A 3000-pixel-wide image printed 10 inches wide is 300 DPI; the same file printed on a 10-foot banner is 25 DPI. Nothing about the file changed — the size did. This is why 'the logo is 300 DPI' means nothing without a size attached.
Working floors for signage: around 150 effective DPI for close-viewed graphics, 100 for banners, and lower is genuinely fine as viewing distance grows. The mistake that fills reprint bins is trusting the metadata number instead of doing the division.
Do the division automatically — print file checker →
Related terms
Software that speaks the trade
PrinterFlo runs print & sign shops on one board — quotes that price by size and material, proofs approved from one link, and a production checklist the quote writes for you.