Calculators: storage space, upload time and scan size

Three calculators: how much space your library will need across all its copies in a few years, how long a first upload takes at your internet speed, and how large your scans will be at the settings this manual uses. All arithmetic; every assumption is listed.

Storage space across your copies

Answers: how big the library will be in a few years at the rate it grew last year, and how much space that is across every copy you keep. Used in One home for your photos and Backups. Read the size now off your phone, computer or photo service (Taking stock says where); for the last 12 months, compare with last year's figure if you wrote one down, or estimate from one month of photos and video times twelve.

Assumptions behind the numbers

• Growth is the last 12 months repeated each year. A new phone, a new baby, more video or a box of scans changes it; rerun the numbers then. Convention
• Three copies is this manual's target (the library and two backups, one away from home), after the 3-2-1 advice the National Archives gives to families. Two copies in different places, the Library of Congress's minimum, is the first milestone. Change the number to your own.
• A gigabyte (GB) here is 1,000 megabytes (MB), and a terabyte (TB) is 1,000 GB, the way drive makers and these services count. A computer may show a slightly smaller figure for the same drive because it counts in powers of 2. Physical principle
• Free amounts as each maker's page stated them on 2026-10-30: iCloud 5 GB; Google 15 GB, shared with Gmail and Drive; OneDrive 5 GB; Amazon Photos 5 GB, with full-resolution photos unlimited for Prime members and videos counted. We give no plan prices; they change. Product-specific

How long a first upload takes

Answers: the fastest a library of a given size can reach a cloud service over your connection. Used in Backups when a cloud service is the copy away from home. Your upload speed is the "upload" figure from an internet speed test run on the network you will use; it is usually much lower than the download figure.

Assumptions behind the numbers

• Hours = GB × 8,000 ÷ megabits per second ÷ 3,600. There are 8 bits in a byte and 1,000 megabytes in a gigabyte, so one GB is 8,000 megabits; an hour is 3,600 seconds. Physical principle
• The result is the fastest possible. Real uploads run slower: the phone sleeps, the app closes, other devices share the line, and services pace large uploads. Treat it as a floor, not a forecast.
• A phone backup usually uploads over Wi-Fi only unless you allow cellular data; check the app's own setting before you count on an overnight upload.

Scan size for prints, slides and negatives

Answers: how many pixels a scan has at a given setting, how large an uncompressed master file is, how much space a whole box takes, and how big a print the scan can make. Used in Prints, slides and negatives. Leave the ppi at 0 to use this manual's setting: 600 ppi for prints and 3000 ppi for film.

Assumptions behind the numbers

• Pixels = size in inches × ppi, on each side. Millimeters convert to inches at 25.4 mm to the inch; a 35 mm frame is 36 by 24 mm. Physical principle
• An uncompressed file takes 3 bytes per pixel at 24-bit color and 6 bytes at 48-bit. A TIFF saved with lossless compression is smaller, and a JPEG sharing copy much smaller. Physical principle
• The settings are this manual's (600 ppi for prints in 24-bit color; 3000 ppi for 35 mm film, or the scanner's highest true optical resolution if lower), chosen from these institutions' figures: the Library of Congress's handout gives 300 ppi for same-size reprints and 400 or 600 to enlarge; the Minnesota Historical Society says 300 ppi is fine in general and 600 for enlargements or precious photos; the federal FADGI guidelines set 400 ppi as their recommended floor for prints and 600 as their highest level, and 3000 ppi as their recommended level for 35 mm film. Convention
• The largest print is the pixel count divided by 300, the print resolution the Library of Congress uses in its reprint rule of thumb and Minnesota uses in its table.
• Use your scanner's true optical resolution, not an "interpolated" figure from the box; a setting above it adds pixels without adding detail (Library of Congress, 2013).