Trying to calculate the strength of a brainwallet created with a custom diceware I want to create a brainwallet using a custom diceware since I don't like the original one. Instead of 7776 words it has 46656 because I use 6 dice for each word instead of 5.

So this is what I got so far, please tell me if I made a mistake:

2 ^ (log2(46656) * 5) / (1 * 10^15) / (60 * 60 * 24 * 365) = 7 years


2 ^ (log2(46656) * 5) is the entropy for a brainwallet of 5 words
1 * 10^15 is 1 Phash/s, which is the hashing power I'm assuming for this attacker. I don't even know if this makes sense, because an attacker doesn't need to start over for each brainwallet he wants to crack.
60 * 60 * 24 * 365 represents a year in seconds
you forgot to divide by 2.

7 years is exhaustive, but on average you'd expect it to take 3.5 years to crack.

10^-15 * 46656^5 seconds / 2