This download time calculator estimates how long a file transfer takes from file size and connection speed.
Other
Download Time Calculator
Estimate download duration from file size and transfer speed.
Calculator
About this calculator
Formula notes
time = file size in bits / speed in bits per second. Remember: 1 byte = 8 bits, and Mbps is megabits, not megabytes.
Worked examples
- Example: a 1 GB file at 100 Mbps takes (8×10⁹ bits)/(10⁸ bps) = 80 seconds, or 1 min 20 s.
- A 4 GB decimal file over a sustained 100 Mbit/s connection takes at least 320 seconds, or about 5 minutes 20 seconds, before overhead.
How to use it
- Enter the file size with its unit.
- Enter the connection speed in Mbps.
- Read the estimated transfer duration.
Frequently asked questions
Why is real download time longer?
Overhead, Wi-Fi loss, and server limits mean real throughput is often 70–90% of the rated speed.
Is 100 MB the same as 100 Mb?
No. MB is megabytes (×8 bits); Mb is megabits. Confusing them makes estimates 8× off.
Limits and interpretation
- Advertised link speed is not sustained application throughput; congestion, Wi-Fi, server limits, and protocol overhead reduce it.
- Bits and bytes and decimal versus binary file sizes must be distinguished or the estimate can be wrong by a large factor.