How to Use the Scan Resolution File Size Calculator
The same Letter-size document can produce wildly different file sizes depending on the scan resolution (DPI) and color mode you choose. DPI stands for dots per inch, the number of pixels packed into each inch of width and height — a higher DPI looks sharper but also means storing far more data. This calculator uses the standard U.S. Letter page size (8.5 x 11 in) and, based on your chosen DPI and color mode, estimates both the raw uncompressed size and the size after typical JPEG compression.
The math multiplies the page's width and height in inches by the DPI to get total pixels, then multiplies by the bits per pixel for your color mode — 24-bit color, 8-bit grayscale, or 1-bit black and white. A color scan at 300 dpi can run into the tens of megabytes uncompressed, but most scanners and scanning apps apply JPEG compression automatically, shrinking the actual saved file considerably.
For everyday paperwork, 150-300 dpi in color or grayscale is usually enough. Reserve 600 dpi or higher for detailed prints or photos you'll need to zoom into — going higher than necessary just eats up storage space without a real benefit.
Frequently Asked Questions
150-200 dpi is plenty for archiving plain text documents, while 300 dpi is the standard choice when you need print-like sharpness. For photos or detailed prints you'll need to zoom into, use 600 dpi or higher.
Most scanners and scanning apps save as JPEG or PDF with compression applied, so the actual file is much smaller than the uncompressed calculation. This calculator also shows a rough estimated JPEG size that accounts for typical compression.