How many clients are typically using Tor simultaneously? How many circuits are simultaneously in use?

From Tor Metrics: Users, I get that there are currently about 2.4 million "directly connecting users". And in Questions and answers about user statistics, I see:

Q: So, are these distinct users per day, average number of users connected
over the day, or what?
A: Average number of concurrent users, estimated from data collected over
a day. We can't say how many distinct users there are.

However, I vaguely recall arguments that the number of simultaneously connected Tor clients, at any given instant, is rather smaller than this estimate, which is calculated as 10% of daily directory requests.

Is there any reason to think that's so?

Also, is it possible to estimate how many circuits are simultaneously in use?

• Dear Mirimir, Do mean on average, or you mean instantaneously, On average you will get a number, but without knowing the distribution function or at least standard deviation of the distribution function it will not tell you much. The interesting case is if the distribution function of number of clients and number of circuits become available as a function of time. (In technical terms, it is called a non stationary stochastic process) From there one may compute almost everything one might want to know about the number of clients and number of circuits at any moment in time.
– Roya
Aug 28, 2014 at 15:49
• @Roya I want to know, like right now, how many other Tor clients have active circuits, with active connections using them. But actually, the mean of that number over a day is enough. By saying "at any given instant", I'm distinguishing what I want from the number of users that were active at some point during a day, but not necessarily at the same time. Aug 28, 2014 at 16:13
• Dear Mirimir, By the way this is an interesting and useful question in my humble opinion. You have my up vote for this question. Have nice time!
– Roya
Aug 28, 2014 at 16:25