How many stormtroopers are in the First Order military?

Question

Approximately how many stormtroopers does the First Order have to throw away? It is mentioned that the current Stormtroopers are better trained than those during the reign of Palpatine, and that the reason for this is that the First Order lacks the insane numerical advantages of the former Empire or those that the New Republic could very easily gain via draft. This implies that both the New Republic and the Galactic Empire were better off in terms of manpower. Furthermore, in a scene on Starkiller base, it shows thousands of Stormtroopers in several large "blocks" (phalanxes?).

Many within the military believed that despite being outnumbered by the New Republic Starfleet, their technological superiority was so complete that even their smaller navy stood virtually unchallenged.

and

With the First Order lacking the numerical superiority of the Galactic Empire, better equipped and trained soldiers resulted in higher trooper proficiency than the previous Galactic Empire.

Are the quotes I am talking about from the all-knowing nearly-all-knowing Wookieepedia.

Answer 1

TL;DR: We don't know from current canon. From 7-15 thousand to 12 million.

• Estimate #1: Upper bound by designation

  Stormtrooper IDs seem to mostly be LL-NNNN form in First Order.

  That gives us a plausible upper limit of 34*34*10,000 = 11,560,000 (11 million troopers) if using Aurebesh letters; or 6,760,000 (~7 million) using English alphabet

• Estimate #2 - Lower Bound (visible during speech)

  There appear to be ~70-100 company-sized blocks of ~100 (actually, 8x12=96) troopers watching in the plaza during Hux's speech.

  That puts us at ~7-10K visible troopers.

  This overshoots the estimate a bit because some of the formations have visibly less troopers in them; and some appear to be non-stormtroopers (black uniforms instead of ST armor - pilots?).

  On the other hand, that likely undershoots the estimate, since (1) there are also STs manning the many walkers around and more importantly (2) Clearly at least some STs are deployed elsewhere, even if we assume the best case scenario of most of STs being in the plaza for the historic speech, for some morale reason.

  

Answer 2

Star Wars episode 7 does not exactly disclose the amount of stormtroopers on Starkiller base and even thought that there are a great amount of troops visible in Hux's speech, we can assume that the planet itself has other outpost and facilities. Also take in the fact that there are still a great amount of troops within the planet and in these possible and tactically logical outposts, and the troops in the new Star Destroyer. So given this information there can be at least guessing around a tens of thousands of troops seen in the film but remember they are still growing and have troops in the unknown reason of space.