A shoebox of family prints looks like nothing on the shelf. Digitize it, and those prints quietly turn into tens of gigabytes of image files — or hundreds, if you pick the wrong settings. The surprise is that the file size is almost entirely in your control: the scan resolution, the color depth and the file format decide whether a single photo costs you 2 MB or 300 MB.
Scanning everything at maximum quality can drown a project in terabytes, while scanning too small leaves files that look soft when reprinted. Before you start feeding a few hundred prints into a flatbed, a quick storage estimate saves both the disk space and the painful re-scanning later.
How Scan Storage Math Works
The math is straightforward multiplication. A scan's pixel count is the print's width and height in inches, each multiplied by the DPI. A 4x6 inch print at 600 DPI becomes 2,400 x 3,600 pixels — about 8.6 megapixels.
Multiply those pixels by the bytes each pixel needs, and you get the raw size:
- 24-bit color (standard): 3 bytes per pixel
- 48-bit color (archival): 6 bytes per pixel — double the standard
- 8-bit grayscale: 1 byte per pixel — ideal for black-and-white prints
The file format then shrinks that raw number. Uncompressed TIFF keeps everything; compressed TIFF roughly halves it; PNG keeps about 60 percent; high-quality JPEG keeps roughly a quarter — at the cost of some editing headroom. Multiply the per-scan size by your photo count and you have the project's total.
The formula: width (inches) x DPI x height (inches) x DPI x bytes per pixel x format factor = file size. A 4x6 print at 600 DPI in 24-bit color works out to about 24.7 MB as an uncompressed TIFF.
DPI Is the Biggest Lever You Have
Doubling the DPI quadruples the pixel count — and the file size. That makes the resolution choice the single most important setting decision of the whole project:
- 300 DPI — fine for photos you will only ever view on screen, roughly 6.2 MB per 4x6 scan as TIFF
- 600 DPI — the sweet spot for standard prints; captures everything the paper holds (about 24.7 MB per 4x6 TIFF)
- 1200 DPI — reserve for small originals like 35mm negatives and slides; a 4x6 at 1200 DPI balloons to roughly 98.9 MB
- 2400 DPI — negatives and slides only; a 4x6 would approach 400 MB
Scanning a 4x6 print at 1200 DPI mostly just quadruples the file without adding real detail — the paper grain, not the image, is all the extra pixels are recording.
Storage Per Scan by Setting
The table below shows approximate file sizes for common print sizes as uncompressed TIFFs in 24-bit color — the heaviest, archive-grade case:
| Print size | 300 DPI | 600 DPI | 1200 DPI |
|---|---|---|---|
| 4 x 6 inch | ~6.2 MB | ~24.7 MB | ~98.9 MB |
| 5 x 7 inch | ~9.0 MB | ~36.0 MB | ~144 MB |
| 8 x 10 inch | ~20.6 MB | ~82.4 MB | ~329.6 MB |
Switching to high-quality JPEG cuts each of these to roughly a quarter — the 4x6 at 600 DPI drops from 24.7 MB to about 6.2 MB. Scanning in 48-bit archival color doubles them instead.
Worked Example: 200 Family Prints
Say you have 200 family prints, all 4x6 inches, scanned at 600 DPI in 24-bit color as uncompressed TIFFs. Each scan is 24.7 MB, so the whole batch needs about 4.8 GB — trivial for any modern drive.
At 2 minutes per photo on a flatbed scanner, that is roughly 6.7 hours of scanning — basically a full weekend afternoon. A 500 GB external drive holds this project easily, with about 495.2 GB to spare; it could hold around 20,712 photos at these settings.
But push the same 200 prints to 8x10 size at 1200 DPI and each scan balloons to 329.6 MB — 500 of those would need 160.9 GB. That is why the DPI decision matters more than anything else.
File Format: Archive Master vs Everyday Copy
The practical workflow most archivists recommend is two files per photo:
- A TIFF master (48-bit if your scanner supports it) — the permanent archive copy with maximum editing headroom
- A JPEG copy — the everyday version for viewing, sharing and uploading
You can always make a small file from a big one, but never the reverse. Disk space is cheap compared to the years those photos represent.
Budget the Time Honestly
Storage is only half the project; the other half is hours. Two minutes per scan sounds fast until you multiply it by a thousand — 1,000 photos take around 33 hours of active scanning on a typical flatbed, realistically spread over several weekends.
- Scan in batches by year or album so partial progress is usable
- Name files with dates and people as you go — a "scan now, organize later" pile becomes a second project
- Handle fragile originals on a flatbed even if a sheet-fed scanner is faster; the speed is not worth a tear
- Clean the scanner glass between sessions — dust becomes thousands of retouching spots
Storage Planning Checklist
Before the first scan, decide: your print sizes, your DPI, your color depth and your format. Then estimate the total and buy or free up at least double that space — one copy is no copy. The calculator below handles the arithmetic:
Try it now: Photo Scan Storage Calculator — enter your print size, DPI, color depth and file format to get exact per-scan and total storage needs.
Frequently Asked Questions
What DPI should I scan old photos at?
600 DPI is the sweet spot for standard prints — it captures everything the paper holds without bloating files. Use 1200 DPI or higher only for small originals like 35mm negatives and slides, and 300 DPI is fine for photos you will only ever view on screen.
Is TIFF or JPEG better for scanning photos?
TIFF is better for archiving because it keeps every pixel your scanner captured, which matters if you ever want to edit or reprint. JPEG files are roughly a quarter the size and perfectly fine for sharing and viewing — many people keep a TIFF master and a JPEG copy for everyday use.
How long does it take to scan 1,000 photos?
At about 2 minutes per photo on a typical flatbed scanner, 1,000 photos take around 33 hours of active scanning — realistically spread over several weekends. A sheet-fed scanner with a photo feeder can cut that to under a minute per photo, but fragile originals should always go on a flatbed.