The Beer Alcohol Content Calculator determines ABV from original gravity (OG) and final gravity (FG) using the standard homebrewing formula (OG − FG) × 131.25. The most fundamental measurement in brewing — giving the true fermentation result that hydrometer readings alone provide.
5.51
%
4.35
%
137
kcal
80.8
%
5
%
0.51
pp
5.51
%
4.35
%
137
kcal
80.8
%
5
%
0.51
pp
Hydrometer readings before and after fermentation are the homebrewer's primary evidence that fermentation occurred — and the gravity drop between them converts directly to the alcohol content of the finished beer. The calculator for beer alcohol content applies the standard brewing formula to give accurate ABV from specific gravity measurements, and compares the result against the typical ABV range for common beer styles to confirm the fermentation performed as expected.
Two formulas are in widespread use for homebrewing:
Simple formula: ABV = (OG − FG) × 131.25
This is accurate within ±0.2% ABV for beers in the normal range (OG 1.040–1.080). For OG 1.060 and FG 1.012: ABV = (1.060 − 1.012) × 131.25 = 0.048 × 131.25 = 6.3% ABV.
More accurate formula: ABV = (76.08 × (OG − FG)) / (1.775 − OG) × (FG / 0.794)
This formula is more accurate for high-gravity beers (OG above 1.080) and for precise ABV determination required for commercial beer labeling. For homebrewing purposes, the simple formula is adequate. Use this online calculator for either formula. The beer brewing calculator estimates pre-fermentation target gravities from recipe ingredients.
Specific gravity (SG) is a dimensionless ratio of liquid density to water density. For beer wort, the dissolved sugars increase density above 1.000 (pure water at 4°C). American homebrewers use SG units (1.050); European and commercial brewers often use the Plato scale (°P), where °P ≈ (SG − 1) × 1,000 / 4. A 1.048 SG wort ≈ 12 °P. Refractometers measure in Brix (very close to Plato); hydrometers measure SG directly. Temperature affects SG readings — most hydrometers are calibrated at 60°F (15.6°C); correct readings taken at other temperatures using the manufacturer's correction table. A reading taken at 70°F on a 60°F-calibrated hydrometer underestimates the actual SG by approximately 0.001.
Apparent attenuation (AA%) = (OG − FG) / (OG − 1.000) × 100 measures how much of the original wort sugar the yeast converted, using hydrometer readings directly. True attenuation accounts for the fact that alcohol is less dense than water, making FG hydrometers reading appear lower than the true residual sugar content. For most homebrewing purposes, apparent attenuation is sufficient. Commercial brewers use true attenuation for accurate alcohol content labeling — important because US TTB (Alcohol and Tobacco Tax and Trade Bureau) regulations permit a 0.3% ABV tolerance on beer labels, making accurate measurement legally significant. The ABV calculator and beverage calculators provide related alcohol content tools.
Final gravity depends on yeast strain attenuation and wort fermentability. Most ale yeasts attenuate 73–80% of apparent attenuation; lager strains 77–84%. Predicted FG = OG − (OG − 1.000) × attenuation fraction. For OG 1.060 with 75% apparent attenuation: FG = 1.060 − 0.060 × 0.75 = 1.060 − 0.045 = 1.015. Actual FG significantly above predicted value (e.g., 1.022 when 1.014 was expected) indicates stuck fermentation — possible causes include: insufficient yeast pitch rate, temperature drop killing yeast activity, lack of yeast nutrients, or highly unfermentable dextrins from mash temperature above 67°C (153°F).
ABV = (OG − FG) × 131.25. ABW = ABV × 0.789. Calories from alcohol = ABV × 2.5 × 3.55 (per 12 oz). Calories from residual carbs = (FG − 1.000) × 1000 × 0.82 × 3.55 × 0.04 (approximated from extract remaining). Total calories = alcohol calories + carb calories. Style midpoints are fixed reference values for contextual comparison: lager 4.5%, ale 5.0%, IPA 6.5%, stout 5.5%, wheat 4.8%, sour 4.5%, barleywine 10.0%.
ABV within 0.5% of your style midpoint indicates on-target fermentation. ABV significantly below target suggests low mash efficiency, incomplete fermentation, or higher-than-intended FG. ABV significantly above target indicates a higher OG than planned or better-than-expected attenuation. For competition beers, check BJCP style guidelines for exact ABV ranges. For calorie-conscious brewing, high attenuation (low FG) reduces carb calories but high ABV increases alcohol calories.
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Results
(1.052 − 1.010) × 131.25 = 5.51% ABV. ABW = 5.51 × 0.789 = 4.35%. Style midpoint for ale is 5.0% — this pale ale is slightly above typical strength, consistent with an American Pale Ale (4.5–6.2% BJCP range).
Inputs
Results
(1.110 − 1.022) × 131.25 = 11.55% ABV. Well above the standard stout midpoint (5.5%), clearly in Imperial Stout territory (BJCP: 8–12% ABV). High FG of 1.022 contributes to full-body and residual sweetness typical of the style.
ABV (Alcohol by Volume) measures the percentage of pure ethanol by volume in the total beverage. ABW (Alcohol by Weight) measures the percentage of ethanol by mass. Since ethanol is less dense than water (0.789 g/mL vs. 1.0 g/mL), ABW is always lower than ABV. ABW = ABV × 0.789. A 5% ABV beer is 3.95% ABW. Most countries and labels use ABV; ABW labeling was historically required for some US state regulations.
For hydrometer readings: (1) Allow the wort to cool to within 10°F of your hydrometer's calibration temperature (usually 60°F/15.6°C); (2) Fill a hydrometer tube with wort, avoiding foam; (3) Gently spin the hydrometer to dislodge air bubbles; (4) Read at the bottom of the meniscus at eye level; (5) Apply temperature correction if the sample is warmer than calibration temp. Many homebrewers use a refractometer for quick OG checks due to its small sample size requirement.
High FG (low attenuation) can result from: (1) low mash temperature producing unfermentable dextrins; (2) insufficient or unhealthy yeast pitch; (3) fermentation temperature too low; (4) lack of nutrients; (5) high adjunct percentage (oatmeal, crystal malts, lactose) that does not ferment; (6) recipe designed for body (e.g., sweet stout with lactose FG target 1.020+). Always compare your FG to the yeast strain's stated attenuation range (typically 65–85%).
A 12 oz craft IPA at 6.5% ABV typically contains 180–220 kcal. The alcohol contributes the majority (~155 kcal), with residual malt sugars adding 25–65 kcal depending on FG. Dry-hopped IPAs with very low FG (high attenuation) can be at the lower end; hazy/New England IPAs with higher FG from oats and wheat additions can run 220–250 kcal. Compare this to a standard Budweiser (145 kcal) or Bud Light (110 kcal).
Commercial breweries use laboratory methods (ebulliometry, gas chromatography) for precise ABV measurement rather than gravity-based formulas. These methods are accurate to ±0.1% ABV, while gravity formulas have ±0.3–0.5% inherent error. Additionally, commercial beers are carbonated and filtered, affecting final density. For homebrewing purposes, gravity-based ABV is sufficiently accurate. If you need certified ABV (for competitions or legal labeling), use a certified laboratory.
A session beer is typically defined as having ABV below 4.5% (UK definition) or below 5% (US craft standard), intended for extended social consumption without rapid intoxication. Session IPAs, session stouts, and mild ales fall in this category. The term comes from UK pub culture where workers were allowed designated drinking 'sessions' — the beer needed to be low enough in alcohol to consume multiple pints without impairment. This calculator can identify session strength by comparing ABV to the 4.5% threshold.
Yes — any water/sugar fermentation works with this formula. Hard seltzers (starting at OG 1.035–1.040, finishing at 1.000–1.002) calculate accurately. Kombucha (low-alcohol fermentation, OG ~1.025, FG ~1.004) would show approximately 2.7% ABV from calculation, though actual ABV of commercial kombucha is usually under 0.5% due to pH and acid production reducing fermentation efficiency. For hard cider, the formula is accurate.
Degrees Plato (°P) is a concentration scale used by commercial breweries, expressing dissolved solids as equivalent sucrose percentage by weight. Conversion: °P ≈ (SG − 1) × 250. For example, OG 1.052 ≈ 13°P. Many craft breweries list original extract in degrees Plato on labels. ABV from Plato: ABV ≈ (OE − AE) × 0.5925, where OE = original extract and AE = apparent extract in Plato. This is equivalent to the standard gravity-based formula.
Any fermentable sugar addition raises OG and therefore potential ABV. Fruit added during secondary fermentation adds sugars that yeast continue to ferment, lowering FG and raising ABV. Taking a gravity reading before and after fruit addition and comparing FG readings allows you to track the additional alcohol contribution. Honey additions in brewing add ~45 gravity points per pound per gallon. Lactose and maltodextrin are non-fermentable and raise FG without contributing to ABV.
No. Hops contribute alpha acids (bitterness), aroma compounds, and preservative oils to beer, but these are measured independently as IBU (International Bitterness Units) and do not affect specific gravity or ABV calculations. A highly-hopped double IPA will have the same ABV calculation method as a minimally-hopped lager. The only way hops can indirectly affect gravity is through dry hop additions, which can release very small amounts of fermentable sugars — but this effect is negligible (less than 0.1°P).
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