Beer ABV Calculator
Calculate beer ABV (alcohol by volume) from Original Gravity + Final Gravity. Standard + alternative formulas, attenuation %, calorie estimate, style advisory.
Beer ABV Calculator
How to use the Beer ABV Calculator
Measure Original Gravity before pitching yeast
OG (Original Gravity) is the specific gravity of your wort (unfermented beer) just before adding yeast. Measure with a calibrated hydrometer floating in a sample jar (or with a refractometer + temperature correction). Typical OG ranges by style: light lager 1.040-1.048; pale ale 1.048-1.056; IPA 1.055-1.075; imperial stout 1.080-1.100; barley wine 1.085-1.120. Record this — it's the only way to calculate ABV later.
Measure Final Gravity when fermentation is complete
FG (Final Gravity) is the specific gravity after fermentation stops — when bubbles in the airlock slow to once every 60+ seconds AND gravity readings on two consecutive days are identical. Typical FG: 1.008-1.018 for most ales (70-80% attenuation); 1.000-1.006 for very dry beers (Saison, Brut IPA, wild ferments); 1.020-1.028 for sweet/big beers (Doppelbock, sweet stouts). Don't bottle until FG is stable — bottling early causes carbonation bombs.
Read your ABV — two formulas shown
The standard formula ABV = (OG − FG) × 131.25 is what most homebrew calculators use; accurate to ±0.3% ABV for OG below 1.080. The alternative formula ((76.08 × (OG−FG) / (1.775−OG)) × (FG/0.794)) accounts for the non-linear relationship at higher gravities; use it for beers above 1.080 OG (Imperial Stout, Barley Wine, Belgian Quad, Eisbock). Below 1.080, both formulas agree within 0.2%.
Check attenuation to evaluate fermentation health
Apparent attenuation = (OG − FG) / (OG − 1). Tells you how much of the available sugars the yeast consumed. Healthy ranges: 65-75% for British / American ales; 75-85% for German / lager strains; 80-90%+ for Belgian / Saison / Brett strains. If attenuation is under 60%, fermentation may be stuck — try raising temp 2-4°C, gentle swirling, or adding fresh yeast. The advisory below the results flags stuck or unusually high attenuation automatically.
Brewing math — how OG, FG, and gravity readings actually work
Specific Gravity (SG) measures the density of a liquid compared to pure water (1.000). When you dissolve fermentable sugars from malted barley into water, the resulting wort has SG > 1.000 — typically 1.040-1.080 for most beer styles. Yeast converts those sugars into ~equal parts CO₂ and alcohol, both of which weigh less than the sugars they replaced. So gravity DROPS as fermentation proceeds. The difference between Original Gravity (before fermentation) and Final Gravity (after fermentation) tells you how much sugar got converted, and from that, how much alcohol was produced. The standard formula ABV = (OG − FG) × 131.25 captures this relationship for typical beers; the multiplier accounts for the density change ratio between sugar and alcohol in water.
Why two formulas matter
The 131.25 multiplier in the standard formula is an empirical fit calibrated against beers with OG in the 1.040-1.070 range — the vast majority of commercial and homebrew styles. At very high gravities (1.080+), the relationship becomes non-linear because: (1) sugar concentration affects yeast metabolism (yeast under stress at high osmotic pressure shifts metabolite profile); (2) the alcohol's density correction becomes significant; (3) residual unfermented sugars contribute to FG in ways that vary by mash temperature. The alternative formula (Berry / Daniels formula) accounts for these effects and gives more accurate ABV for Imperial Stouts (OG 1.090+), Barley Wines (1.100+), and Eisbocks (1.120+). For an OG of 1.100 + FG 1.025: standard says 9.84%; alternative says 10.43%. The 0.6% difference matters for legal-label accuracy.
For 95% of beers (OG below 1.080), the standard ABV formula works. For Imperial styles, use the alternative formula — at high gravities, the standard formula underreports by 0.5-1% ABV.
Attenuation — the single best fermentation diagnostic
Apparent attenuation = (OG − FG) / (OG − 1), expressed as percentage. It measures how "completely" the yeast fermented the available sugars. 50-65%: low attenuation, sweet finish, possibly under-attenuated (stuck fermentation, low-attenuation yeast strain like English Ale, or intentional sweetness like Milk Stout). 65-78%: typical attenuation for British / American ales, lagers. The "sweet spot" for most beer styles. 78-85%: high attenuation, dry finish, typical for German lagers + clean American yeasts. 85-95%: very high attenuation, very dry, characteristic of Belgian / Saison / Champagne / Brett yeasts. 95%+: indicates contamination by wild yeast or bacteria that ate dextrins the brewing yeast couldn't reach. Attenuation below 60% with healthy yeast is almost always a stuck fermentation — try gentle agitation, raising temp, or adding a tiny pitch of fresh yeast. Attenuation above 90% in beer using only normal ale/lager yeast suggests Brett or bacterial contamination.
The ASEAN homebrew + craft beer angle
Homebrewing and craft beer have grown rapidly across ASEAN over the past decade. Singapore: legal to homebrew up to 30L/month for personal use without license (since 2019); thriving craft brewery scene (RedDot, Brewlander, Trouble Brewing, Pink Blossoms, Off Day, Smith Street Taps). Homebrew supplies via Brewerkz Homebrew, online via iHerb / Lazada. Malaysia: homebrewing exists in a legal grey area; the well-established craft scene includes Tigerfish, BCMNI Brewing, Sapporo (Malaysian production). Thailand: famously restrictive on small-scale brewing (the famous 2017 reform attempts); craft beer is brewed offshore (Vietnam, Cambodia) and imported. Vietnam / Philippines: rapidly growing craft scenes (Pasteur Street Brewing, East West Brewing in HCMC; Crows / Engkanto in Manila). Tropical brewing challenges: ambient 28-32°C is too warm for clean ale fermentation; either invest in a fermentation chamber (modified mini-fridge with Inkbird controller is the standard hack) or stick to high-temp tolerant strains (Belgian, Saison, kveik). The math in this calculator applies identically — but ASEAN homebrewers should pay extra attention to temperature control + yeast strain selection, since the climate is unforgiving.
10 Things to Know About Beer ABV
The standard ABV formula ABV = (OG − FG) × 131.25 is an empirical fit calibrated against beers with OG 1.040-1.070 — the vast majority of styles.
For high-gravity beers (OG > 1.080), use the alternative formula — at 10%+ ABV, the standard formula underreports by 0.5-1% ABV.
Apparent attenuation % is the best fermentation diagnostic. 70-85% is healthy. Below 60% = stuck. Above 90% = wild yeast or Brett.
Specific Gravity (SG) measures density vs pure water. 1.050 wort is 5% denser than water — the extra mass is dissolved sugar from malt.
The Plato scale is what commercial brewers use globally — it expresses sugar content as % by weight. 12°P ≈ 1.048 SG.
Hydrometers measure SG by buoyancy. Calibrated at 20°C / 68°F — readings at other temps need correction (warmer = lower reading).
Refractometers measure SG by light bending (Brix). Pre-fermentation: accurate. Post-fermentation: requires alcohol correction (~1.04× factor).
The world's strongest beer is Snake Venom by Brewmeister at 67.5% ABV — made by repeated freezing and removing ice (concentrating alcohol).
Most yeast strains can't survive above 12% ABV. Special high-alcohol strains (Champagne, Belgian Trappist, distiller's yeasts) reach 18-20%.
Beer calories come from alcohol + residual sugars. A 5% ABV beer is roughly 150 cal/12oz; an 8% Imperial Stout is ~300+ cal/12oz.
Frequently Asked Questions
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OG (Original Gravity) is the specific gravity of wort BEFORE fermentation — measures how much fermentable sugar is present. FG (Final Gravity) is the specific gravity AFTER fermentation — measures what's left after yeast consumed the sugars. The drop from OG to FG is what got converted to alcohol + CO₂. Both readings are taken with a hydrometer or refractometer floating in a sample of wort / beer at a calibrated temperature (usually 20°C / 68°F).
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Both, depending on OG. Standard formula: accurate ±0.3% ABV for OG 1.040-1.080 (which covers 95% of beer styles). Use this for pale ales, IPAs, lagers, wheat beers, porters, regular stouts, Saisons under 7.5% ABV. Alternative formula: more accurate at OG above 1.080 — use for Imperial Stouts, Double IPAs, Barley Wines, Belgian Quads, Eisbocks. For a 1.100 OG beer the two formulas can disagree by 0.5-1.0% ABV; for legal/regulatory accuracy, use the alternative formula at high gravities.
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Depends on yeast strain. English Ale yeasts (Wyeast 1968, Whitelabs WLP002): 67-75%. American Ale (Wyeast 1056, WLP001, Safale US-05): 73-77%. German Lager (Wyeast 2124, WLP830): 73-78%. Belgian Saison (Wyeast 3711, Lalbrew Belle Saison): 80-95%. Champagne / wine yeast: 90-95%+. The Wyeast / White Labs / Fermentis specsheets list expected attenuation for each strain. If your attenuation is well below the strain's expected range, fermentation might be stuck.
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"Stuck fermentation" means yeast stopped before reaching expected FG. Symptoms: FG is 5-15 points above predicted, attenuation below 60%, airlock has been quiet for days but gravity won't drop. Try in order: (1) Raise ambient temperature 2-4°C — cold yeast goes dormant. (2) Gently swirl the carboy to rouse settled yeast. (3) Wait 3-5 days; sometimes lagers just need patience. (4) Pitch a starter of fresh yeast — use a "neutral" strain like US-05 or Champagne yeast for safety. (5) Check for infection (sour smell, pellicle) — if so, the beer is probably lost. Don't bottle until gravity is stable for 2 consecutive days.
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Liquid density changes with temperature — warmer liquids are less dense, so the hydrometer floats lower and reads lower SG than reality. Hydrometers are calibrated for 60°F (15.5°C) or 68°F (20°C) — check the label. For readings at other temps, use correction tables: at 30°C / 86°F, add ~0.002 to your reading; at 40°C / 104°F, add ~0.004. Most hydrometers come with a correction chart in the box. Refractometers have their own temperature correction (usually built in for Brix scales).
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Yes, with a correction. Refractometers measure how light bends in the sample, which is proportional to sugar content (in Brix or SG) BEFORE fermentation. After fermentation, the alcohol present also bends light, throwing off the reading. The standard correction factor is ~1.04× — i.e. divide your post-ferment refractometer SG by ~1.04 to get true SG. Better: use formulas like Sean Terrill's refractometer correction calculator that account for OG too. Hydrometers don't have this issue; many homebrewers use refractometer for OG (small sample needed) and hydrometer for FG (more accurate post-ferment).
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Three different scales for the same thing — dissolved sugar content. Specific Gravity (SG): ratio vs pure water (1.000 = water). 1.048 = beer wort with 12% sugar by weight. Used by homebrewers. Plato (°P): percentage of sugar by weight. 12°P ≈ 1.048 SG. Used by professional brewers globally. Brix: same as Plato (both express weight-percent of sucrose-equivalent), used in winemaking. For beer brewing, the three are interchangeable; pick one and stick with it. This calculator's output table shows the equivalent in Plato/Brix.
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Three critical things: (1) High OG (1.080-1.100+) requires more grain — a 10% Imperial Stout needs 6-7 kg malt per 20L batch. (2) Pitch 2-3× normal yeast — high-alcohol environments are stressful, you need a large healthy colony. Make a yeast starter 1-2 days before brew day. (3) Oxygenate well — yeast needs oxygen at the start for healthy cell membranes that survive high alcohol. Shake the wort vigorously for 5+ minutes or use pure O₂ for 60 seconds. (4) Pick an alcohol-tolerant strain — Wyeast 1056, WLP001, Safale US-05 handle up to 11%; for 12%+ use Champagne yeast (Lalvin EC-1118) or specialty Belgian strains.
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No. All calculations run entirely in your browser via JavaScript. There's no server roundtrip — open DevTools → Network and confirm zero outbound requests. Your gravity readings stay on your device. Safe for proprietary commercial brewery formulations, homebrew competition recipes, or any brewing IP that shouldn't leave your machine.
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Varies. Singapore: legal up to 30L/month for personal use since 2019, no license needed. Malaysia: grey area; small-scale homebrew for personal consumption typically not enforced but technically requires license. Thailand: famously restrictive — most small-scale brewing is illegal under current alcohol production laws, although reform efforts continue. Vietnam / Philippines / Indonesia: generally permissive for small personal-use brewing. Brunei: complete ban on alcohol. Always check current local regulations before brewing. The math in this calculator is universal — but always brew within your jurisdiction's rules.
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