Since anty’s calculator seems to be down, I recently wrote my own calculator:

http://xpm.muuttuja.org/calc/

It uses the same formula I originally posted in January:

https://bitcointalk.org/index.php?topic=255782.msg4431354#msg4431354

[quote=“mikaelh”]blocks/day = chains/day * (0.97 * (1 - fracDiff) + 0.03)

Here fracDiff is the fractional part of the difficulty, i.e. fracDiff = diff - floor(diff).

This is simply assuming that it’s a 0.03 probability for the (k+1)'th number being prime in a chain. These result in longer chains which are not subject to the fractional difficulty. This number was produced by the function EstimateNormalPrimeProbability() in my latest code. It’s a bit smaller than my previous estimate of 0.035 being the probability.[/quote]