Twenty to twenty-five. That is the answer, and if that is all you came for you can stop reading. But the count is the least important variable here, and optimising it while ignoring the rest is why most people's hashtags do nothing.
Size beats quantity
Put a post in #food and you are joining half a billion others. Your
post occupies the top of the recent feed for roughly four seconds before being
buried. You have spent a slot and gained nothing.
Put the same post in a tag with fifty thousand entries and you can hold the top of that feed for hours. Fewer people are browsing it, but they chose that tag deliberately, which is why smaller tags convert into follows and saves at a much higher rate than large ones.
A working set uses both, weighted heavily toward the middle: a few large tags in case something catches, a majority of mid-size tags where you can realistically rank, and a handful of very specific ones that keep working for days after the post drops out of everything else. the tag builder groups them by competition; the tiering is the entire point of it.
What changed
Hashtags used to be the discovery mechanism. Now they are one input among many, and not the strongest one. Reach comes primarily from the recommendation engine, which decides who sees your post based on watch time, saves, shares and how similar accounts have responded to similar content.
That has led to a lot of "hashtags are dead" content, which overstates it. What they still do is tell Instagram what the post is about (useful signal for a system deciding who might want to see it) and they still drive genuine traffic inside smaller niches, where the recommendation engine has less data to work with and the tag feed is still a real browsing surface.
They are no longer the lever. They are still worth pulling.
Placement does not matter
The advice about hiding tags in the first comment has been repeated for a decade and Instagram has now stated directly that placement has no effect on reach.
Put them wherever keeps the caption readable. That is the only thing the choice affects. If your caption is short and the tags would swamp it, first comment. If the caption is long, nobody notices them at the end anyway.
Rotate, or they stop working
Pasting an identical block of thirty tags onto every post is a pattern Instagram's spam detection looks for explicitly. It rarely produces anything as clear as a ban. It produces a gradual decline in reach that is almost impossible to diagnose from the inside, because nothing tells you it has happened.
Changing roughly a third between posts avoids it, and has a useful side effect: you find out which tags actually pull. Check the insights panel a few days after posting and look at reach from hashtags. Tags that never appear there are not working for you, whatever their follower count suggests.
Banned tags are a real risk
Instagram restricts a long, unpublished, constantly moving list. Some entries
are obviously problematic. Many are ordinary words that got overrun with spam.
#desk, #valentinesday and #adulting have all
been on it at various points, which tells you the list is about moderation load
rather than the word itself.
One restricted tag can suppress the entire post. Checking takes five seconds: search the tag inside Instagram, and if the recent posts section is missing or a warning notice appears, drop it.
What actually moves reach
Since we are being honest about the ceiling here: hashtags are a rounding error next to the things that genuinely determine how far a post travels.
Watch time, first. A reel people finish, or rewatch, gets pushed. One they swipe past in two seconds does not, and no tag set rescues it.
Saves and shares, second. Both are stronger signals than likes because both cost the viewer something. Content people send to a friend travels; content people tap a heart on mostly does not.
Consistency, third, not in the "post daily or die" sense, but in the sense that an account posting recognisably similar things gives the recommendation engine a clear audience to match against.
Hashtags support all of that. They do not substitute for any of it. Spend twenty minutes on your first three seconds before you spend twenty minutes on your tag set.