Transfer duration and usable data rate
The transfer estimate applies equally to upload and download when the entered bandwidth is the rate for that direction. Use a measured sustained rate where possible. Time does not include establishing a connection or processing the completed file.
If the transferable file is an encoded video with a known bitrate, the Video File Size Calculator can estimate its size before the transfer calculation.
The formula
Network bandwidth is entered in megabits per second, while file size uses bytes. Eight bits make one byte. The throughput share reduces the advertised rate to an assumed usable transfer rate, and time assumes that rate remains constant.
Worked example
A 1 GB file contains 1,000,000,000 bytes. At 100 Mbps with 80% usable throughput, the effective rate is 10 MB/s. Transfer time is 100 seconds, or 1.667 minutes. A 1 GiB file under the same assumptions takes 107.374 seconds.
How to use this calculator
- Enter file size, file-size unit using the units shown.
- Set connection bandwidth, usable throughput share.
- Calculate and review estimated transfer time alongside the supporting quantities.
Bits and bytes change the apparent speed
Internet plans commonly describe rates in Mbps, while applications may show MB/s. The uppercase B represents bytes; lowercase b represents bits. GB and GiB also differ because one uses decimal powers and the other binary powers. Selecting the unit that matches the file measurement prevents a size mismatch before the throughput allowance is applied.
The slowest part of a transfer matters
A server limit, Wi-Fi interference, shared traffic, storage performance, or congestion can reduce the effective transfer rate. The throughput input provides a single planning assumption rather than measuring these conditions. Very small files can spend more time in connection setup than data transfer. Large transfers may experience changing speed, retries, or pauses that extend completion.
Assumptions & limitations
What this calculation assumes
- The usable transfer rate is constant throughout the file.
What to keep in mind
- Excludes connection setup, retries, interruptions, server processing, and fluctuating network rates.
Common questions
Can I calculate upload time?
Yes. Enter your upload bandwidth, which may differ from the download rate.
Why does GiB take longer than GB?
A GiB contains 1,073,741,824 bytes, more than the 1,000,000,000 bytes in a decimal GB.
Should I enter a displayed MB/s value as Mbps?
No. Multiply decimal megabytes per second by eight to obtain megabits per second before entering bandwidth.
Sources & further reading
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