ABV Calculator
Estimate alcohol content using original and final gravity. Perfect for brewers monitoring fermentation.
Measure before fermentation begins.
Measure after fermentation completes.
Optional quick correction for hydrometer readings above calibration temp (60°F).
ABV
5.25%
ABW
4.15%
Apparent Attenuation
80.0%
Corrected ABV
5.25%
How to Use This Calculator
Measure your original gravity (OG)
Use a hydrometer or refractometer before fermentation to capture sugar density in your wort or must.
Capture final gravity (FG)
After fermentation finishes, take another gravity reading to see how much sugar was converted to alcohol.
Review ABV, ABW, and attenuation
Use the results to confirm target strength, fermentation performance, and label accuracy.
Formula
ABV (%) = (OG - FG) × 131.25
ABW (%) = ABV × 0.79
Apparent attenuation (%) = (OG - FG) ÷ (OG - 1) × 100
Example: OG 1.060 and FG 1.012 → (1.060 - 1.012) × 131.25 = 6.30% ABV.
Tip: Always degas samples and ensure instruments are calibrated at 60°F (15.6°C) for accuracy.
Full Description
Alcohol by volume (ABV) measures the percentage of alcohol in your finished beverage. By comparing gravity before and after fermentation, you can determine how efficiently yeast converted sugars into alcohol. This calculator also shows alcohol by weight (ABW) and apparent attenuation to help diagnose fermentation issues and confirm recipe targets.
Homebrewers and winemakers rely on ABV calculations to accurately label brews, plan blends, and ensure legal compliance. The optional temperature correction accounts for hydrometer readings taken above calibration temperature. For precision, cool samples or use temperature correction tables provided by instrument manufacturers.
When this tool is essential
- Verifying recipe targets during brew day and packaging.
- Troubleshooting stuck fermentations via attenuation readings.
- Comparing strength across batches or styles.
- Estimating taxes or compliance reporting for commercial breweries.
Remember that residual sugars, adjunct use, and measurement error can all affect ABV estimates. For absolute accuracy, official labs use distillation or gas chromatography—but this calculation is reliable for everyday brewing decisions.
Frequently Asked Questions
Why is my ABV lower than expected?
Yeast health, fermentation temperature, and mash efficiency affect attenuation. Check aeration, nutrients, and mash schedule.
Can I calculate ABV from Brix?
Yes. Convert Brix to specific gravity (SG) first or use a refractometer correction calculator for more accurate results.
What if my FG is higher than OG?
This indicates a measurement error. Recalibrate tools and ensure samples are degassed and at the correct temperature.
How do I label ABV legally?
Regulations vary by region. Recreational brewers estimate within ±0.3%; commercial producers should confirm with certified labs.