It seems both of those calculators are better than the rule of thumb from Driver's Ed 20 years ago: 1 beer per hour per 100 pounds == .10 BAC
Which led me to think 1 beer per 2 hours per 100 pounds would be close.
Aparently, I was wrong, though on the safe / conservative side

From the calculators:
http://www.ou.edu/oupd/bac.htm1 per hour for a 100 pound male = .04
1 per hour for a 160 pound male = .02
1 per hour for a 240 pound male = .01
http://www.dot.wisconsin.gov/safety/mot ... ulator.htm1 per hour for a 100 pound male = .026
1 per hour for a 160 pound male = .012
1 per hour for a 240 pound male = .004
2 per hour for a 300 pound male = .013
So yes, drinking slowly (socially and responsibly) even a 100 pound man can drink one drink in an hour and be below BAC depending on your calculations.