Last updated: July 16, 2026
ABV Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
The ABV Calculator converts original and final gravity readings to alcohol by volume percentage using the standard homebrewing formula ABV = (OG − FG) × 131.25, as well as the more precise Balling-derived advanced formula. It supports specific gravity, degrees Plato, and Brix input units, calculates apparent attenuation, total alcohol weight for a given batch volume, and provides the equivalent extract in degrees Plato.
To calculate ABV, subtract your final gravity from your original gravity and multiply by 131.25. For example, OG 1.055 minus FG 1.010 equals 0.045; multiplied by 131.25 gives 5.91% alcohol by volume.
Key Takeaways
- ABV = (OG − FG) × 131.25 is the standard simple formula, accurate to ±0.5% for beers under 8% ABV.
- The advanced Balling formula is more accurate for high-gravity beers and wines above 8% ABV.
- Degrees Plato and Brix are automatically converted to specific gravity before calculation.
- Apparent attenuation shows how efficiently your yeast converted fermentable sugars to alcohol.
- Alcohol weight in your batch equals volume (L) × ABV/100 × 0.789 (density of ethanol).
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
ABV (%) = (OG − FG) × 131.25
Where:
- OG=Original Gravity(SG)
- FG=Final Gravity(SG)
- ABV=Alcohol by Volume(%)
Worked Examples
Classic American Pale Ale
A standard homebrewed APA with OG 1.055 and FG 1.010 measured in specific gravity.
- 1Measure OG = 1.055 SG before pitching yeast
- 2After fermentation, measure FG = 1.010 SG
- 3Apply simple formula: ABV = (1.055 − 1.010) × 131.25
- 4ABV = 0.045 × 131.25 = 5.91%
- 5Attenuation = (1.055−1.010)/(1.055−1) × 100 = 81.8%
Strong Belgian Tripel (Advanced Method)
High-gravity Belgian beer; the advanced formula accounts for actual extract utilisation.
- 1OG = 1.080, FG = 1.016
- 2Advanced: ABV = (76.08 × (1.080−1.016) / (1.775−1.080)) × (1.016/0.794)
- 3= (76.08 × 0.064 / 0.695) × 1.280
- 4= 7.007 × 1.280 ≈ 8.97%
- 5Alcohol weight for 20 L: 20 × 0.0897 × 0.789 ≈ 1.415 kg
Homebrew Cider in Plato
Cider brewer using a refractometer reading in °Plato for OG and FG.
- 1OG = 13.0 °P → SG ≈ 1.0529 using SG = 1 + (13.0 / (258.6 − (13.0/258.2)×227.1))
- 2FG = 3.0 °P → SG ≈ 1.0121
- 3Simple ABV = (1.0529 − 1.0121) × 131.25 = 0.0408 × 131.25 ≈ 5.35%
Introduction
The ABV Calculator determines the alcohol content of your homebrew beer, wine, cider, or mead from two simple gravity readings — original gravity (OG) and final gravity (FG). As yeast ferments sugars into ethanol and CO₂, the liquid becomes less dense, and that drop in gravity directly reveals how much alcohol was produced. Whether you measure in specific gravity, degrees Plato, or Brix, this calculator converts all units automatically and offers both the quick simple formula (±0.5%) and the more precise advanced formula (±0.1%) derived from Balling’s original work.
How ABV Is Calculated from Gravity
Specific gravity (SG) measures how much denser a liquid is compared to water (SG 1.000). Wort or juice containing dissolved sugars might start at SG 1.050; as yeast consumes those sugars, the gravity falls toward 1.010 or lower. The difference — called the gravity drop — is directly proportional to the ethanol produced. The simple formula, ABV = (OG − FG) × 131.25, is a linear approximation derived from the fact that each gravity point drop corresponds to roughly 0.131% ABV. The constant 131.25 accounts for the density of ethanol (0.789 g/mL) and the relationship between extract and alcohol yield. For high-gravity beers or wine (OG > 1.070), the advanced Balling-derived formula is more accurate because it accounts for the changing density of the fermenting wort.
Simple vs. Advanced Formula
Simple formula: ABV = (OG − FG) × 131.25. Fast and reliable for typical homebrew strengths (ABV 3–8%). Error is ±0.3–0.5% absolute. Advanced formula (Balling/Tabarie): ABV = (76.08 × (OG − FG) / (1.775 − OG)) × (FG / 0.794). This accounts for the residual extract in the finished beer and the actual density of the ethanol-water mixture. Use the advanced formula for any beer above 8% ABV. Both methods work hand-in-hand with the Priming Sugar Calculator for post-fermentation carbonation and the Alcohol Dilution Calculator for blending batches to a target ABV.
Understanding Gravity Units: SG, Plato, and Brix
Three scales are used to express wort density: - Specific Gravity (SG): Dimensionless ratio to water. Water = 1.000; typical wort 1.040–1.100. - Degrees Plato (°P): Grams of sucrose per 100 g solution. Roughly °P ≈ (SG − 1) × 259. Conversion: SG = 1 + (°P / (258.6 − (°P/258.2)×227.1)). - Brix (°Bx): Historically identical to Plato for pure sucrose; used in winemaking with refractometers. The same formula applies. This calculator applies the precise Plato-to-SG polynomial before running the ABV formula. For wine-specific calculations, see the SO₂ Wine Calculator. More information on gravity scales is available from the American Society of Brewing Chemists.
Attenuation: How Efficiently Did Your Yeast Work?
Apparent attenuation = ((OG − FG) / (OG − 1)) × 100. It expresses what percentage of the original extract was fermented. A reading of 75% is typical for most ale yeasts; lager strains and high-attenuating strains can reach 85–90%. Higher attenuation produces a drier, stronger beer. Very high attenuation (>90%) may indicate infection, over-pitching, or a highly fermentable wort. For more context on fermentation chemistry, see Bamforth’s Beer: Tap into the Art and Science of Brewing (Oxford University Press).
Practical Tips for Accurate Gravity Measurements
1. Temperature correction: Hydrometers are calibrated at 60°F (15.6°C). At 68°F add ~0.001 to the reading. 2. Sample preparation: Degas wort/beer before measuring — CO₂ bubbles attach to the hydrometer and give false high readings. 3. Sanitise everything: Contaminated test cylinders introduce infection and skew readings. 4. Take duplicate readings: Average two readings 24 hours apart to confirm fermentation is truly complete. 5. Refractometer FG correction: Alcohol refracts differently from sugar; apply a correction before using Brix for final gravity. See the Party Drink Calculator for planning alcohol quantities and the Beer Pong Calculator for party serving estimates. Official measurement methods are documented by NIST.
ABV Ranges for Common Beer and Cider Styles
Understanding expected ABV for each style helps verify whether your measurements are realistic: | Style | OG Range | FG Range | ABV Range | |---|---|---|---| | Session Ale | 1.030–1.040 | 1.006–1.010 | 3.0–4.2% | | American Pale Ale | 1.044–1.060 | 1.008–1.014 | 4.5–6.2% | | India Pale Ale | 1.056–1.075 | 1.008–1.018 | 5.5–7.5% | | Belgian Tripel | 1.075–1.095 | 1.008–1.018 | 7.5–9.5% | | Imperial Stout | 1.075–1.115 | 1.018–1.030 | 7.0–12.0% | | Dry Cider | 1.045–1.065 | 0.999–1.010 | 4.5–7.0% | Style data from the BJCP 2021 Style Guidelines.
Quick Reference Card
ABV Quick Reference Cheat Sheet
Quick reference • ABV Calculator
ABV (%) = (OG − FG) × 131.25Valid range: OG: 1.025–1.120 SG | FG: 0.995–1.030 SG | ABV: 0–15%
Common Values
⚠ Watch Out
- •OG must always be greater than FG — if not, fermentation is incomplete or the reading is wrong.
- •Temperature affects hydrometer readings — correct for temperature deviation from the calibration point (usually 60°F/15.6°C).
- •Refractometer FG readings must be corrected for alcohol content before using in ABV formulas.
- •Brix and Plato use the same conversion formula for pure sucrose, but wort contains other sugars — minor error (<0.1%) is expected.
Pro Tips
- →Degas your sample (swirl or let rest) before measuring — CO₂ bubbles cause falsely high hydrometer readings.
- →Average two gravity readings 48 hours apart to confirm fermentation is truly finished before calculating final ABV.
- →For wine or high-sugar cider, use the advanced formula — it more accurately models the higher initial sugar concentration.
- →Keep a fermentation log: recording OG, FG, temperature, and yeast strain across batches helps you predict ABV before fermentation ends.
FAQs
Why does my ABV calculation seem too high?
The most common cause is an inaccurate FG reading. If fermentation is still active, your FG will be higher than the true final value. Wait until the gravity has been stable for 48 hours. Also check that your hydrometer is temperature-compensated. Another cause is using Brix values directly without applying the alcohol correction to the final-gravity reading.
What is the difference between simple and advanced ABV formulas?
The simple formula (ABV = (OG−FG)×131.25) is a linear approximation accurate to ±0.5% for beers up to ~8% ABV. The advanced formula (Balling-derived) is more accurate for high-gravity and strong beers because it accounts for the changing density of the ethanol-water mixture and residual extract.
Can I use a refractometer to measure final gravity?
Yes, but you must apply an alcohol correction because ethanol bends light differently than sugar water. Use the correction: FG_SG ≈ 1.0000 − 0.00443×Brix + 0.000119×Brix². Without this correction, a refractometer FG reading is misleadingly high, and the calculated ABV will be falsely low.
What does apparent attenuation mean?
Apparent attenuation is the percentage of the original fermentable extract that was consumed by yeast: ((OG−FG)/(OG−1))×100. It’s called ‘apparent’ because the hydrometer is fooled by the lower density of ethanol, making fermentation look slightly more complete than it truly is. Typical ale yeasts attenuate 72–80%; highly attenuative strains can reach 85–90%.
How do I convert degrees Plato or Brix to specific gravity?
Use the polynomial formula: SG = 1 + (°P / (258.6 − (°P/258.2)×227.1)). For example, 12°P → SG ≈ 1.0483. This calculator applies this conversion automatically when you select the Plato or Brix gravity unit.
How much alcohol is in my batch by weight?
Enter your batch volume and unit in the optional volume fields. The calculator computes: alcohol weight (kg) = volume (L) × (ABV/100) × 0.789, where 0.789 g/mL is the density of ethanol. For example, a 20-litre batch at 5.91% ABV contains 20 × 0.0591 × 0.789 ≈ 0.933 kg of pure ethanol.