Gbit/s stands for gigabits per second, and it is the unit USB-IF and most manufacturers use to state the maximum data rate of a USB or Thunderbolt connection. USB 3.2 Gen 1 runs at 5 Gbit/s, Gen 2 at 10 Gbit/s, Gen 2x2 at 20 Gbit/s, and USB4 at 20, 40, or with USB4 Version 2.0, up to 80 Gbit/s.
It is worth remembering that Gbit/s measures bits, not bytes, and that real world file transfer speeds, usually shown in megabytes per second by an operating system, will be noticeably lower than the raw Gbit/s figure once overhead and unit conversion are taken into account. A connection rated at 10 Gbit/s, for example, translates to a theoretical maximum well under 1.25 gigabytes per second in practice.
Comparing two cables or devices by their stated Gbit/s figure is a reliable way to judge relative speed, as long as the whole chain, port, cable and device, matches that rating. See our guide to USB speeds for a full breakdown.
