Download time calculator

Enter the file size and your connection speed. The answer assumes the download gets your full line speed; the notes below explain why real downloads often take longer.

The Lynx team Checked 3 min read

13 min 20 s at 12.5 MB/s, the full speed of a 100 Mbps line

The short version

Time = file size ÷ speed. Convert both to the same unit first: internet speeds are in megabits (Mbps), file sizes in megabytes (MB), and 1 byte is 8 bits. A 10 GB file on a 100 Mbps line: 10,000 MB × 8 ÷ 100 Mbps = 800 seconds, about 13 minutes.

How to calculate download time

  1. File size in bits: multiply megabytes by 8. 1 GB = 1,000 MB = 8,000 megabits.
  2. Divide by your speed in megabits per second. That’s the time in seconds.
  3. Don’t know your speed? On a Mac, open Terminal and run networkQuality. It prints your downlink capacity in Mbps.

Download times at common speeds

At full line speed, start to finish:

File size10 Mbps50 Mbps100 Mbps300 Mbps1 Gbps
1 GB13 min 20 s2 min 40 s1 min 20 s27 s8 s
5 GB1 h 06 min13 min 20 s6 min 40 s2 min 13 s40 s
20 GB4 h 26 min53 min 20 s26 min 40 s8 min 53 s2 min 40 s
50 GB11 h 06 min2 h 13 min1 h 06 min22 min 13 s6 min 40 s
100 GB22 h 13 min4 h 26 min2 h 13 min44 min 27 s13 min 20 s

Why real downloads take longer

  • Overhead. A few percent of every connection goes to the network’s own bookkeeping, so even a perfect download lands a little under your plan’s number.
  • A shared line. Backups, updates and streaming on any device on your network take their share.
  • Wi-Fi. Distance and walls can cut your speed well below what the plan delivers to the router.
  • The server. A busy or far-away server, or one that caps each connection, can be the slowest link. A download manager that fetches several parts of a file at once often gets around a per-connection cap.

What to do about each one: downloads slow on your Mac? How to make them faster. And if a long download keeps failing partway, see how to download large files on a Mac.

Questions

How long does it take to download 1 GB?
At 100 Mbps, about 1 min 20 s. At 50 Mbps, about 2 min 40 s, and at 10 Mbps about 13 min 20 s. That assumes the download runs at your full line speed the whole time.
How long does it take to download 100 GB?
At 100 Mbps, about 2 h 13 min. At 300 Mbps, about 44 min 27 s; at 500 Mbps about 26 min 40 s; at 1 Gbps about 13 min 20 s, at full line speed the whole way. Big game and system downloads often run slower than your line because the server is busy.
What’s the difference between Mbps and MB/s?
Internet plans are sold in megabits per second (Mbps); browsers and download managers show megabytes per second (MB/s). A byte is 8 bits, so divide Mbps by 8: a 100 Mbps line moves at most 12.5 MB/s.
Why does my download take longer than the calculator says?
The calculator assumes the download uses your whole line from start to finish. In practice a few percent goes to network overhead, other devices share the line, and the server you download from may be slower than your connection. See how to speed up downloads on a Mac.
Is a GB 1,000 or 1,024 megabytes?
This calculator uses 1 GB = 1,000 MB, like macOS Finder and disk makers. Some apps use 1,024 (strictly a GiB); the difference is about 7 % at gigabyte sizes.

Sources

Checked on October 2, 2026. If something here is out of date, tell us.

  1. NIST: Prefixes for binary multiples: GB vs GiB
  2. Apple Support: How storage capacity is measured on Apple devices: macOS counts 1 GB as 1,000,000,000 bytes

More guides

All guides
Guide · Big downloads How to download large files on a Mac Check space and drive format, keep the Mac awake, resume in Safari or Chrome, and verify the file with a checksum. Guide · Big downloads Downloads slow on your Mac? How to make them faster Measure your line with networkQuality, fix what’s on your side, and learn when more connections help. Guide · Big downloads Safari can’t resume this download: what to do Where the Resume button is, what the .download file is, and why Safari sometimes starts again from zero.