Olddial-upmodems supported data rates up to 56 Kbps, for example.
Most data pipe equipment features Mbps speed ratings.
High-end gear features Gbps speed rating:
What Comes After Gbps?

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1000 Gbps equals 1 terabit per second (Tbps).
Few technologies for Tbps speed networking exist today.
you’re free to do the calculations yourself manually or use any of a number of online calculators.
For example, you’re able to convert Kbps to Mbps with those rules.
So 15,000 Kbps = 15 Mbps because there are 1,000 kilobits in each 1 megabit.
CheckYourMathis a cool calculator that supports data rate conversions if you want to try them on your own.