It will be buried in the FMC performance, and will be different all the time due to weight, wind, etc. As others have suggested the best you can use is a rule of thumb. Another way is simply to work out if the FMC is low on profile during the descent to the respective WPT then obviously it has 'fat' built in to slow down, if there's not much fat expect a "DRAG REQUIRED" FMC message.