What is Mbps vs MB?

Mbps measures how fast data moves, while MB measures how much data there is. Internet providers advertise speeds in Mbps, with a small b for bits. Files are measured in MB or GB, with a capital B for bytes. Since a byte is eight bits, divide Mbps by 8 to get megabytes per second.

A 100 Mbps connection moves at most about 12.5 MB per second. A 1 GB file would then take roughly 80 seconds in ideal conditions, and longer in practice.

Upload speed matters most when sending. Many home connections upload far slower than they download, so check your upload figure when planning a big transfer.

Best-case times, using 1 GB = 1,000 MB = 8,000 megabits:

Real uploads are usually slower because of Wi-Fi, other devices on the network and distance to the server, so add some margin.

1. Convert the size to megabits: 4 GB × 8,000 = 32,000 megabits.
2. Divide by the speed: 32,000 ÷ 20 = 1,600 seconds.
3. Convert to minutes: 1,600 ÷ 60 = about 27 minutes.

If your speed test shows 20 Mbps download but only 5 Mbps upload, use the 5: the same file would take four times as long, about 1 hour 47 minutes.

Most internet speeds and many storage makers use decimal units, where 1 GB is 1,000,000,000 bytes. Windows measures in binary units, where its GB is 1,073,741,824 bytes, but still writes GB. So a file Windows calls 1 GB is about 7% bigger in decimal terms, while macOS uses decimal units. The difference is small, but it explains why sizes do not always match between devices.