Understanding SAS transfer speeds

I've been tasked with building some large storage and i'm first working to expand my SAS knowledge. As i consider transfer bottlenecks and SAS speeds, i can't help but wonder how 12 Gb/s SAS equates to 4800 MB/s of transfer. From a pure conversion standpoint those numbers don't equate, so i assume it has to do with theoretical vs actual speeds? Or is it just that 12 Gb/s is simply the name of the SAS standard, and this standard is 4800 MB/s of transfer? Thanks for helping me clarify.

12Gbps is just an interface speed. Think of it as a link-speed (like Gigabit or 10GbE). Your individual drives will not be capable of 12Gbps transfers. It's just the next step up in the SAS protocol. 3Gbps, 6Gbps, 12Gbps...

This will help with oversubscription in certain external exclosure situations, but without more detail on what you're doing, this is the general idea.