I was talking to a staff at NB recently and he suggested a way to estimate alcohol content based on his experience (and emphasized this was not scientific).
He suggested that if you put a decimal point b/w the last two digits of the OG, this will be very close to the ABV (E.g. NB’s White House Honey Porter’s OG is 1.054. Therefore, according to his method, the final alcohol content would be @ 5.4%)
Denny’s right as usual it will depend on the FG for it to get you 5.4% ABV it will have to finish at 1.013, if it finishes at say 1.018 your ABV will be 4.72 %
The above estimation method is pretty darn close for most beers. In fact, using a little statistical mathematics on all of my own batches, on the average, this method comes short by about 0.1% alcohol. So for a 1.050 beer, I should expect a beer of about 5.1% alcohol, etc. There is a lot of variation in the data, but the vast majority of data points come within 0.4% of the true alcohol level, which is close enough for me.