Formula
The usable speed is the typed speed times what remains after overhead:
seconds = bytes × 8 / (Mbps × (1 − overhead) × 1,000,000)
A gigabyte here is 1,000,000,000 bytes. The download page divides by the full speed.
Assumptions
- Overhead stays at the percent you type.
- The file size is decimal gigabytes.
- The clock rounds to the nearest second.
Worked example
A 2 GB upload at 50 Mbps with 10% overhead takes 5:56.
Input definitions
- Overhead
- The share of the line that does not carry the file, such as acknowledgements.
- Upload speed
- Megabits per second before that share is removed.
Limitations
This is a planning figure from the numbers you type. It is not a measurement of a network, a camera, a printer, or a power supply.
Questions
Why is this slower than the download page?
The same 50 Mbps is reduced by 10% here, so the division uses 45 Mbps. The download page uses the full 50.
What overhead should I type?
Ten percent is a planning allowance. Use a smaller number only if you have measured the useful share of the line.