The Correct Answer is:

I realize a many individuals trust he’s around 8’5″, however he said he was dead. (“… and now that I’m dead, I might eliminate my cap and present Shakespearean statements”) So, he must be alive eventually, and it’s unlikely that he developed to godlike level while living. Despite the fact that he seems, by all accounts, to be very tall, I would assess him to be around 6’5″, yet that is essentially the way in which tall he showed up in the film. In any case, soon after the film’s delivery, an item named a “day to day existence size cardboard pattern” of Jack Skellington with a level of 5’10” was delivered, subsequently it’s entirely conceivable that is his level.