Diceware

The total entropy of a password with words is bits;
The total number of combinations with this number of words is (the dictionary contains words);
Time to crack using brute force, investigating 50% of the total combinations

Assuming 1,000,000,000,000,000 words/second
(government standard, 1 quadrillion/sec):
.

Assuming 1,000,000,000,000 words/second
(industry standard, 1 trillion/sec):
.