At the end of the day it comes down to one factor: A higher Signal-to-Noise Ration (SNR) will produce a higher data rate.
I have two sites bookmarked in my web browser to remind me of those requirements.
Both authors have obviously done an incredible amount of research to gather the data so I absolutely in no way pretend to have put together this myself. The Receive Sensitivity/RSSI requirements have been compiled from various sources and should only be used as a guide as each vendor radio will have their own specifications.
Anyway... I got tired of flicking between the two sites above so I decided to create a chart that merges the two. It has become my one stop shop for quickly determining the SNR requirements for a required throughput (I lie, there are two charts, one for 802.11n and one for 802.11ac.)
I recommend having a read of the first post. Andrew Von Nagy has done an amazing job on explaining the how MCS rates are achieved...
I welcome all feedback!