Unknown, but 20,000 seems a safe bet
------------------------------------

To the best of my knowledge, the specific number of midi-chlorians that Luke possesses has not been stated in current Disney canon. That said, some interviews with George Lucas can shed some limited light on the matter. 

According to an [interview][1] with George Lucas in *Rolling Stone*. 

> You got it. And when he finds out Luke is his son, his first impulse
> is to figure out a way of getting him to join him to kill the Emperor.
> That’s what Siths do! He tries it with anybody he thinks might be more
> powerful, which is what the Emperor was looking for in the first
> place: somebody who would be more powerful than he was and could help
> him rule the universe. But Obi-Wan screwed that up by cutting off his
> arms and legs and burning him up. **From then on, he wasn’t as strong as
> the Emperor – he was like Darth Maul or Count Dooku. He wasn’t what he
> was supposed to become. But the son could become that.**

And, perhaps [even more clearly][2]:


>“Anakin, as Skywalker, as a human being, was going to be extremely
> powerful,” he says. “But he ended up losing his arms and a leg and
> became partly a robot. So a lot of his ability to use the Force, a lot
> of his powers, are curbed at this point, because, as a living form,
> there’s not that much of him left. So his ability to be twice as good
> as the Emperor disappeared, and now he’s maybe 20 percent less than
> the Emperor. **So that isn’t what the Emperor had in mind. He wanted
> this really super guy, but that got derailed by Obi-Wan. So he finds
> that, with Luke, he can get a more primo version if he can turn Luke
> to the Dark Side.”**

This pretty clearly implies that Luke could become what Anakin was meant to be:  a Force-user more powerful than Darth Maul, Count Dooku, or Darth Sidious. Luke is simply as “more primo” version of Anakin, unencumbered by loss of limbs or robotization. Anakin with the midi-chlorian levels he had in his youth, in other words. 


**This suggests that Luke was portrayed as having the same general level of power (and perhaps midi-chlorians) as Anakin: 20,000**:


> Qui-Gon took a slow, deep breath and exhaled softly. “What do the
> readings say, Obi-Wan?”
> 
> “They say the midi-chlorian count is twenty thousand.”

><sub>*The Phantom Menace*</sub>

However, one important caveat applies: **now that Disney is in charge of canon, none of this may apply.** That said, it seems that Disney is [generally trying][3] to keep their canon in line with what Lucas wrote, so these statements may be seen as having some canon validity. Further, some of the top people associated with the new canon, such as J.J. Abrams, [have suggested][4] that they don’t want to question Lucas’s pronouncements:


> I will just say this: **I would never presume to question anything
> George Lucas says is canon in Star Wars.** And our job was not to negate
> or undo. A lot of people who are critics of our Star Trek, and I
> respect all of them, said we destroyed what they loved and negated
> everything. And we worked hard to clarify that we are not saying that
> our Star Trek over-rides a thing of the original Star Trek — it was a
> parallel timeline. I never wanted to negate canon that fans held so
> dear. And because I love Star Wars and have for too many years… … And
> having said all that and meaning it — **I don’t want to presume
> over-write or change what George says the rules are.**



Further, what *is* canon has showed Luke managed some pretty impressive feats, such as apparently deflecting an explosion using the Force (*Shattered Empire*):

[![enter image description here][5]][5]


And of course, the fact that Luke defeated Vader in lightsaber combat after giving into his anger is still quite canonical, giving us some evidence that he is stronger than Vader’s level of power as of the original trilogy. 


  [1]: http://www.rollingstone.com/movies/news/george-lucas-and-the-cult-of-darth-vader-20050602
  [2]: http://www.vanityfair.com/news/2005/02/star-wars-george-lucas-story
  [3]: https://scifi.stackexchange.com/questions/910/how-is-canonicity-of-derivative-works-determined-for-star-wars
  [4]: http://www.slashfilm.com/jj-abrams-midi-chlorians/
  [5]: https://i.sstatic.net/aS5uU.jpg