Hydrometer: how to use



  • Apparent Attenuation: the percentage of sugars that the yeast consumes.

  • It's always a good idea to take a hydrometer reading before you rack into your secondary fermenter. This is good because you can check the amount of sugars the yeast has already consumed. What you are looking for in this reading is an apparent attenuation percentage of 70-75%. 
    • NOTE: Each strain of yeast has its own attenuation.
  • Temperature affects your reading, taking a reading at 70°, for example, would change your reading +0.001. 
  • It's a good idea to calibrate your hydrometer in 60° distilled water when you get it. Ideally it would float at 1.000. This number should not change, but a variance of 0.001 can affect your readings.
  • Formula for alcohol percentage:
    • Specific Gravity - Final Gravity x 131.25 = % Alcohol
      • Ex. 1.065 - 1.015 x 131.25 = 6.56% ABV