If you divide by the time reqd to send the data then you would get the underlying PHY rate, but if you want the MAC (or higher) throughput then you need to include the time for RTS, CTS, ACK (and may be even the TCP ack).

Thanks everyone for your responses. Very helpful indeed.

We ware planning to implement the standard defined by IEEE 802.11 and are focused on MAC layer. So, were wondering how the standard IEEE 802.11 data rate is defined.

I understand that according to Shannon's formula, with better SNR, achieved rate will be higher. But if we think about practical implementation, it will be limited by the  corresponding modulation and coding index defined by the standard (along with other factors that you mentioned already). For example, if for any system, if 16QAM is the highest index of modulation, no matter how much received SINR is estimated, data rate will be limited by 4bps/Hz.

Data rate is defined based on the Symbol rate number of bits and the error correction scheme used. Thus the data rate will vary depend on modulation scheme , coding rate and symbol duration (Symbol rate ), depend on sub carriers the symbol rate will change.

Without RTS/CTS

𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡𝑖𝑚𝑒 𝑝𝑒𝑟 𝑝𝑎𝑐𝑘𝑒𝑡 = 𝐷𝐼𝐹𝑆 + 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐵𝑎𝑐𝑘𝑜𝑓𝑓 𝑡𝑖𝑚𝑒 + 𝑃𝑎𝑐𝑘𝑒𝑡 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒 + 𝑆𝐼𝐹𝑆 + 𝐴𝑐𝑘 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒

With RTS/CTS

𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝑡𝑖𝑚𝑒 𝑝𝑒𝑟 𝑝𝑎𝑐𝑘𝑒𝑡 = 𝐷𝐼𝐹𝑆+ 𝑅𝑇𝑆 𝑃𝑎𝑐𝑘𝑒𝑡 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒+𝐶𝑇𝑆 𝑃𝑎𝑐𝑘𝑒𝑡 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒+ 𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐵𝑎𝑐𝑘𝑜𝑓𝑓 𝑡𝑖𝑚𝑒 + 𝑃𝑎𝑐𝑘𝑒𝑡 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒 + 𝑆𝐼𝐹𝑆 + 𝐴𝑐𝑘 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑇𝑖𝑚𝑒

And in these forumula, the control packets (RTS, CTS, ACK) are sent at the broadcast (lowest rate) while the packets can be sent at a rate determined by RSSI & SNR.