How much data do Mtalk calls consume?

During a call Mtalk will consume approximately 24 kbps per channel, that is about 176 kB per 1 minute of conversation and for each direction (incoming and outgoind). 

Therefore the overall data usage will be 352 kB per minute. Data usage refer to default settings, regardless the call is HD or SD.

Data usage when Mtalk is on stanby  is rather negligible.