Best File Size for Scanned Photos: Keep, Share and Upscale

It depends on whether the file is a master or a copy. A master should keep every pixel the scanner captured. A copy only needs enough pixels for the screen or sheet it will land on. The Library of Congress’s own personal scanning guide (read 11 October 2026) says documents are generally scanned at 300 dpi, photographs you intend to enlarge to 8 by 10 inches or more at 400 or 600 dpi, and that “anything above 600 may be unnecessary”.

File size follows from arithmetic, not taste. Pixels equal inches times dpi on each side, and an uncompressed 8-bit color TIFF stores 3 bytes per pixel. That is why the sizes below climb so fast: doubling the dpi quadruples the pixels.

A 16-bit TIFF doubles those figures, and lossless compression inside the TIFF (LZW or Zip) cuts them by an amount that depends on the picture. The Library of Congress’s Signal blog says the right resolution “depends” on the original, and recommends 300 dpi/ppi for common print sizes; our starting point: 600 dpi for prints up to 5 by 7, 300 to 400 for larger ones, for anything you cannot rescan.

Why a 4 × 6 print rarely needs more than 600 dpi

At 600 dpi a 4 by 6 gives 8.64 megapixels. Doubling to 1200 dpi quadruples the pixels and the file size, and the Library of Congress says anything above 600 may be unnecessary.

Share small JPEG copies, and match their pixel size to the place that receives them. Email, iCloud and Google Photos each cap something different, and the cap is often pixels, not bytes.

Check which version your album was made on; Apple’s page splits the rules by it. When the receiving service resizes for you, a smaller copy saves upload time and loses nothing on display. For a shared drive or a USB stick, a 2000 pixel JPEG is enough for the screen and for a 4 by 6 reprint at 300 dpi (1200 × 1800).

Photos you plan to post publicly deserve a privacy pass first; see what to check before you post a photo. Check metadata before you post.

Keep a TIFF as the master and make JPEGs from it. The Library of Congress’s Mike Ashenfelder writes that “it is a good practice to save the scan as a TIFF, rather than as a JPEG or PDF”, because TIFF is lossless and can hold up to 16 bits per channel where JPEG holds 8. His sharing advice is a JPEG copy, with the TIFF always kept.

The cost is size. In our TIFF to JPG measurements, a 300 dpi test page was 25,249,952 bytes uncompressed. LZW compression inside the TIFF cut it to 4,507,252 bytes, losslessly, and a JPEG at quality 75 (made with sips) reached 1,830,824 bytes. That was one synthetic invoice page, not a photograph, so a photo will compress less.

The Library of Congress’s personal-scanning guide is more relaxed: for color photos it says to save a medium-quality JPEG, and the high-quality setting if you plan to reprint. If disk space is short, a high-quality JPEG master is defensible; if you may ever restore the photo, keep the TIFF. Smol has no lossless mode, so it is for the copies, not the master; a lossless repack of a TIFF is a job for your scanning software. Photographers handling bigger shoots can read image compression for photographers.

Start from the use of the copy, then set quality and the maximum dimension. The numbers below are starting points we chose, not measured thresholds; check the largest output each time.

Use Compress, not Convert. Converting a TIFF to JPG ignores the quality setting and writes a large, high-quality file; Compress honors your quality and your pixel limit in one pass. JPEG chroma changes with quality: 4:2:0 up to 75, 4:2:2 at 80 to 85, 4:4:4 from 90, which is why reprint copies sit at 90 and above. Smol’s target-size mode accepts 4 to 4096 KB and takes about 28 seconds for one 768 × 512 image, so keep it for the few files that miss a cap.

For scale, on 24 small high-quality film photos (768 × 512, default settings) Smol made JPEGs 69.3% smaller; the full conditions are on the benchmark page. A 600 dpi scan is a different workload, so read it as direction, not a forecast. Metadata stripping is on by default and removes EXIF, GPS, IPTC and XMP; switch it off if you want those fields kept.

Work from a copy of the folder, and do the whole shoebox in one batch.

1. 1

   Name and back up the masters first

   Descriptive names such as 1962-beach-aunt-rose.tif beat IMG_0412. Keep two copies on separate drives before you touch anything.

2. 2

   Drag the scan folder into Smol

   Smol writes copies with a _compressed suffix next to the originals and never overwrites by default. Whole folders and mixed file types are fine.

3. 3

   Set Compress, output JPG, quality 75 to 85

   Use the settings table above. Set the maximum dimension to 2000 for email or 2048 for Apple albums, or raise it for a copy you will reprint.

4. 4

   Run it and read the per-file sizes

   Smol shows the size of every output. Find the largest. If it clears your email or album limit, so do the rest.

5. 5

   Open two outputs at 100 percent

   Check faces, text on the back of a photo and skies for banding. If they look soft, raise quality 5 points and rerun.

6. 6

   Save the settings as a preset

   Presets are saved on that Mac, so name it something like Family 2000 px and recreate it on another Mac if you share the job.

Yes: Smol upscales images 2×, 3× or 4× and writes PNG, JPG or WebP. It helps when a small scan has to fill a bigger frame or screen. It cannot restore detail the scanner never recorded, so judge the result by eye before replacing anything.

• A 1200 × 1800 scan (4 × 6 at 300 dpi) at 2× becomes 2400 × 3600, the pixel count of the same print at 600 dpi.
• Rescan first if you still have the print. A new scan at 600 dpi captures real detail; upscaling a 300 dpi file cannot.
• Upscale a copy. Keep the original scan and write the larger file as a new name or folder.
• Use PNG for the output if you will edit it again; JPG or WebP if it is the final copy.

For tools aimed at AI art and a closer look at what upscaling can and cannot do, see upscaling AI art, and the Topaz Gigapixel alternatives comparison. Pros who shoot film or deliver to clients will find photographer client delivery useful.

More tools are in the best image compressor for Mac, the head-to-head test against ImageOptim and the Smol versus TinyPNG comparison. For tidy automation, the Finder Quick Action puts compress on a right-click. Family photos are personal files, and Smol uploads nothing; there is no account and no server.

You need a lossless archive. Smol always re-encodes images and has no lossless mode. Your master TIFF should stay as your scanner wrote it; use Smol on copies.

You need restoration. Smol does not remove scratches, fix color fade or colorize. Upscaling adds pixels, not information. Use a photo editor for repair.

You are not on a Mac. Smol runs on macOS only. A Windows laptop or a phone alone cannot run it, so use the sharing services’ own resizing.

You are scanning a few prints. Preview can export a few photos for free. Smol pays off when the shoebox is hundreds of files, or when you do the job every holiday.

You need the files tagged and organized. Smol does not catalog or caption. Do the naming and folders in Finder or a library app, then batch the copies.