The factor: 1,000, not 1,024
1 gigabit per second (Gbps) equals exactly 1,000 megabits per second (Mbps) in this convention — a clean decimal factor, matching how internet and network speeds are conventionally advertised. Likewise, 1 Mbps equals 1,000 kbps.
Bits versus bytes: an extra factor of 8
Connection speeds are advertised in bits per second (Mbps), but file transfer progress is usually shown in bytes per second (MB/s) — and 1 byte is always 8 bits. A 100 Mbps connection converts to 100 ÷ 8 = 12.5 MB/s, which is why a "100 Mbps" plan shows a download speed far lower than 100 in most download managers.
Why this specific confusion is common enough to deserve its own explainer
This bits-versus-bytes mismatch between advertised connection speed and displayed download speed is common enough — and confusing enough — that it's covered in its own dedicated article, which walks through exactly why an internet plan and a download progress bar seem to disagree.
Why transfer rates use a different base than storage sizes
Data storage sizes (KB, MB, GB) traditionally use a 1,024-based binary convention, while data transfer rates use this 1,000-based decimal one — two closely related "data" units that happen to use different scaling conventions, for reasons explored in the companion article on why that split exists.