According to Ev’s interview with Nieman Lab published yesterday (August 30, 2017), each member’s $5.00/month gets distributed amongst all the claps he or she has given that month on locked posts. That means that if you are a member and you clap a total of 5 times in a month on locked posts, each of your claps are worth $1, if you clap 500 times in a month, each of your claps are worth $0.01, and so on. If you clap a total of 5 times in a month—3 times for Post A, 1 time for Post B, and 1 time for Post C, each of your claps would be worth $1 and your $5 would roughly get distributed as $3 to the author of Post A, $1 to the author of Post B, and $1 to the author of Post C (minus any fees Medium charges).
It’s not that the post with the absolute most claps gets the most money. It’s that: If you engage with one author, in the extreme case, all of the money from you goes to that author. If you engage with a thousand of them, that money goes to a thousand of them. It gives more agency to the member and it allows people who may have a small fan base or be in a niche area to still do well, because the majority of their fans’ money will go to them.
In that interview, Ev mentioned that they were still figuring out the exact formula and may include other metrics, but it sounds like from Ev Williams’s parent post that they ended up going with just claps, at least for this first iteration:
Side note: Calculations were entirely based on engagement from members. We sliced the data every which way from Sunday and determined that, while not perfect, claps reflected a pretty reasonable measure of what members want to see.
TL;DR Total claps on a locked post are correlated with how much that post will earn you, but there’s no way to tell a priori how much a clap will be worth. Every member’s clap is worth something different, which you can’t calculate until the end of the month: $5 / # claps on locked posts they give out that month.