How accurate are hydrometers at estimating ABV? We bought a brand new hydrometer and testing tube to test our first ever brew, an oatmeal stout. BeerSmith estimated that it should be near 6.2% ABV. The hydrometer tested at about 2.5% pre secondary fermentation. Does the secondary raise the ABV by that much? Could this estimate have been accurate or was it thrown off by something? We tasted the brew before bottling and it definitely tasted like a higher ABV than 2.5%. Any thoughts for a baby-brewer such as myself?