How to use the hashtag reach calculator
The limitation comes first. No public model turns a hashtag's total post count (say 1.2 million posts) into the reach you will get. Platforms do not disclose how hashtag traffic is distributed, and the same tag behaves differently depending on account size, topical fit and posting time. So this page builds no table of expected impressions by hashtag size. It only lets you compare the hashtag reach your own insights actually recorded.
Open the impression sources breakdown for your posts, then enter how many posts used each hashtag and the reach those posts got from it. The calculator works out reach per post for each tag and lists them in a table. The strongest tag is the one with the highest reach per post, not the largest total: a tag used ten times and a tag used twice cannot be judged on totals alone.
The comparison reflects your own past results and guarantees nothing about future posts. Use at least a month of data, swap out the weakest tags, then measure again the same way. Repeating that loop is what makes hashtag choices data-driven rather than guesswork.
Frequently asked questions
Not reliably. Crowded tags can push your post out of the feed within minutes. Judge by the reach per post measured on your own account instead of by tag size.
Instagram reports a hashtag share inside the impression sources section of post insights. If your account type does not show that breakdown, this comparison is not available to you.