Download time calculator

How long a download or a copy takes, and when it ends by your clock. Any two of size, speed and time give the third, in bits or bytes, in thousands or 1,024s.

Free. No ads, no paid extras, no tracking, no sign-up. Nothing you type here is sent anywhere.

Size, speed and time

Find

Size

Speed

Time

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Real speed, share of the nominal

A shared line and protocol overhead usually cost 5 to 20 percent.

Already done

Time and speed are then for what remains.

Start at

Empty means now. Only the ending time uses it.

Time needed

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The link holds what you changed after the # sign, a part browsers never send to a server; Copy link also puts it in the address bar, so it stays in this browser’s history.

This size at common speeds

Typical speeds, not guaranteed: lines, radio and disks vary. Choose a row to use its speed.

Connection or disk	Typical speed	Time

Already running? Estimate from progress

Total size

Done so far

Time elapsed

Or as h:mm:ss or 1h 15m 30s, the way copy programs show it.

Average speed so far: ---
Time left at that speed: ---
Ends: ---
Progress: ---

Nothing is sent and nothing is stored. Every number is worked out in your browser, and the page makes no request after it has loaded. On zeromile.tools it is served with connect-src 'none', so the browser itself refuses any connection its script might try to open.

How this calculates

Bits and bytes: 1 byte is 8 bits. Internet plans are sold in bits per second (Mbit/s, often written Mbps); download windows show bytes per second. So 100 Mbit/s moves 12.5 MB each second, not 100. Chrome and Firefox count those bytes in 1,024s and still write MB/s: that is the MiB/s figure in the line under the speed.
Thousands and 1,024s: kB, MB, GB, TB and PB count in thousands: 1 GB is 1,000,000,000 bytes, as disks are sold and macOS counts. KiB, MiB, GiB, TiB and PiB count in 1,024s: 1 GiB is 1,073,741,824 bytes. Windows counts in 1,024s but writes KB, MB, GB: a file Windows calls 9.31 GB is 10 GB here.
The sums: Time is size divided by speed; speed is size divided by time; size is speed times time. The real speed share multiplies the speed first. With an amount already done, only what remains counts.
Times: Shown to three units at most (2 h 13 min 20 s; 3 days 4 h 12 min), the last one rounded, and, from 1 s to just under 100 days, as h:mm:ss in the field. A year here is 365 days. Under a millisecond, microseconds (µs) and nanoseconds.
Ending time: By this device’s clock and time zone, on a 24-hour clock, from now or from the start you set. It moves on as the clock does.
Typing numbers: A dot or a comma marks decimals: 1.5 and 1,5 are both one and a half. A comma or a dot is never read as a thousands separator, and spaces are not accepted: write 1500000. Under the size, speed and time fields the number is said again the way it was understood. A unit may follow the number (100 GB, 100 Mbps): it goes into the list beside the field. A time can also be written as h:mm:ss or as 1h 15m 30s.
Common speeds: Typical real speeds, not the best case and not guaranteed. Wired lines lose about 6 percent to packet overhead, so a 100 Mbit/s line gives about 94. Mobile figures are typical national averages. Disks and USB are for large files; many small files go slower.
From progress: Average speed is what is done divided by the time elapsed. Time left is what remains divided by that average: it assumes the rest goes at the same pace.