Download time calculator
File sizes are quoted in bytes and connection speeds in bits per second. The factor of eight between them is where most of the confusion comes from.
Mbit/s
%
%
Transfer time
0:08:03
- In minutes
- 8.05
- In hours
- 0.134
- Effective throughput
- 10.350 MB/s
- Effective link speed
- 82.80 Mbit/s
- Time at the advertised speed
- 0:06:40
Show the working
- File size = 5
- Connection speed = 100
- Protocol overhead = 8
- Share of the link you actually get = 90
- bits = 5 * 8e9 = 40 000 000 000
- Effective link speed = 100 * (1 - 8/100) * 90/100 = 82.8
- Transfer time = 40 000 000 000 / (82.8 * 1e6) = 483.092
- Time at the advertised speed = 40 000 000 000 / (100 * 1e6) = 400
- Effective throughput = 82.8 / 8 = 10.35
- In minutes = 483.092 / 60 = 8.051 53
- In hours = 483.092 / 3600 = 0.134 192
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- time = file size in bits / effective bits per second
- 1 byte = 8 bits, and 1 GB = 10^9 bytes in the decimal convention used by storage vendors
TCP/IP framing costs roughly 5 to 10% of raw link capacity before anything else goes wrong.
A 100 Mbit/s link delivers at most 12.5 MB/s, and realistically nearer 11.