Tip: Figure ABV Without a Starting OG Original Gravity

Part of Our Homebrew Tips and Tricks Series.  Check out the complete list – Homebrewing Tips, Tricks & Shortcuts!


  • Forgot to take an original gravity and still want an estimate of ABV?  No problem.  You’ll need a refractometer and a hydrometer.
  • Take careful measurements with each.  Thoroughly de-gas the sample to get a more accurate reading.
  • Run those numbers through this equation.  SG is the gravity reading obtained from the hydrometer,  Brix is the reading obtained from the refractometer.  ABV = [277.8851 – 277.4(SG) + 0.9956(Brix) + 0.00523(Brix2) + 0.000013(Brix3)] x (SG/0.79).
  • This is a great reason to get a refractometer.  There are many offerings and they can change quickly.  Shop Around, Search Amazon for “dual scale refractometer” to compare prices and see what models are currently available.
  • More reasons to get a refractometer!  See Tip 9.
  • Thanks to BYO for this formula.  Not a subscriber?  Subscribe to BYO
  • Related Categories: FermentationRefractometers

Make sure the components you use are compatible and rated for your intended application.  Contact manufacturer with questions about suitability or a specific application.  Always read and follow manufacturer directions.


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