It's totally impossible to count the total user of bitcoin.
In one way bitcoin is anonymous and in another way in bitcoin world hardly few user usages real info for creating bitcoin wallet. And 1 user usage 1 to 2 or more wallet so it's quite unpredictable to figure out the exact number of bitcoin user. If one want to know then he might have to conduct world wide census.
even with consensus or survey can't give you the right number of people using bitcoin because there's still a big chance you will get the wrong answer,and there's always someone who hiding and keep silence so it's not a good solution i guess, i'm still in my opinion that counting the actual number of people using bitcoin is impossible
yap this is the difficult things to knows because it is very easy to get a bitcoin address so no one will ever know how many are actually using bitcoin.
I would consider as active users those who are using Bitcoin (sending or receiving bitcoins) on at least a weekly basis
In this way, the upper limit of active users could still be reasonably well approximated. If the number of transactions per day equals 400-450k tpd (as determined by the Blockchain stats), it is possible to find out the number of unique addresses used throughout a week. Since the number of those who make offline transactions should be negligible, the result thus obtained should represent the upper limit of the number of active Bitcoin users with a high degree of confidence. Anyone want to find out that figure?