How to use a hydrometer


Simply put, a hydrometer measures the density of liquids.  When it comes to brewing, this is called gravity, and measuring it is how you determine the ABV% (alcohol by volume) of whatever it is you're fermenting.  It also helps you figure out when you're ready to bottle.

  • ON BREW DAY, fill the tube that comes with your hydrometer roughly 3/4 to the top.  If you have one, a sanitized baster is handy for transferring liquid from your fermenter to the tube.  Otherwise, use your sanitized racking cane that comes with your kit.  Do this by putting the racking cane in the liquid, then press your thumb over the top end.  The liquid will stay in the racking cane while you transfer it to the tube.
  • Slowly submerge the hydrometer into the liquid filled tube until the hydrometer floats (note: do this when your liquid is room temperature).  If there are lots of bubbles at the surface, give the hydrometer a gentle spin to help break them up and wait a minute.
  • Record the reading at the top of the liquid.  This is your Original Gravity (OG).  You'll need this number in the future.
  • As your liquid ferments, its gravity changes.  When fermentation is complete, take an additional reading.  This is called your Final Gravity (FG).
  • Enter both your OG and your FG into the calculator below to see what your ABV is.

Alcohol By Volume Calculator:
Gravity Unit:
Original Gravity (OG):
Final Gravity (FG):

(see below for more information)

Alcohol By Volume:
Apparent Attenuation:
163.7 per 12oz bottle
Original Gravity:
12.39 °P, 1.050
Final Gravity:
2.56 °P, 1.010