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Homebrewing
Homebrew ABV & IBU Calculator
Enter your original and final gravity to estimate alcohol by volume, attenuation and calories, then add a hop schedule for Tinseth IBU. Perfect for dialing in your next batch.
Alcohol by volume
5.3%
Apparent attenuation—
Calories per 12 oz—
Bitterness (Tinseth)—
BU:GU ratio—
ABV and IBU, defined
ABV (alcohol by volume) is the percentage of a beverage's volume that is pure alcohol. In homebrewing it is estimated from the drop in sugar density between the original gravity (before fermentation) and the final gravity (after). IBU (international bitterness units) measures perceived hop bitterness; the Tinseth formula estimates it from hop acid content, quantity, boil time and wort gravity.
The formulas
ABV % = (OG − FG) × 131.25
attenuation % = (OG − FG) ÷ (OG − 1) × 100
IBU = (AAdecimal × oz × 7490 × utilization) ÷ gallons
utilization = bigness × boil-time factor
attenuation % = (OG − FG) ÷ (OG − 1) × 100
IBU = (AAdecimal × oz × 7490 × utilization) ÷ gallons
utilization = bigness × boil-time factor
Worked example
With OG 1.050 and FG 1.010: ABV = (1.050 − 1.010) × 131.25 = 5.25%, attenuation = 0.040 ÷ 0.050 = 80%. One ounce of 6.5% hops boiled 60 minutes in 5 gallons gives roughly 24 IBU.
Frequently asked questions
How is ABV calculated from gravity?
ABV = (OG − FG) × 131.25.
What is attenuation?
The percent of sugar fermented: (OG − FG) ÷ (OG − 1) × 100.
How are IBUs calculated?
Via the Tinseth formula from alpha acid, ounces, boil time and gravity.
What gravity readings do I need?
An OG before pitching yeast and an FG when fermentation finishes.
How many calories are in my homebrew?
Estimated per 12 oz from your OG and FG, higher gravity means more calories.