ABV (Alcohol by Volume) measures the percentage of pure alcohol in your beer. The most common formula used by homebrewers is: ABV = (OG - FG) × 131.25. OG (Original Gravity) is measured before fermentation, and FG (Final Gravity) after fermentation completes. The difference represents the sugar consumed by yeast, which is converted to alcohol and CO₂.

Specific Gravity (SG) is a ratio comparing the density of wort/beer to water (water = 1.000). Plato (°P) directly measures the percentage of extract (sugars) by weight. 1°P ≈ 1.004 SG. Professional brewers often use Plato, while homebrewers typically use SG. Both measure the same thing—just different scales. Use whichever your hydrometer or refractometer displays.

Hydrometers are calibrated to a specific temperature (typically 60°F or 20°C). If your wort or beer is at a different temperature, the density reading will be off. Hotter liquid = lower density reading = SG appears lower than actual. For example, wort at 100°F measured with a 60°F-calibrated hydrometer can read ~0.004 lower than actual. Always correct for temperature or cool your sample to calibration temperature for the most accurate results.

Apparent Attenuation (AA) = (OG - FG) / (OG - 1) × 100%. It tells you what percentage of available sugars the yeast consumed. Most ale yeasts have 70-80% attenuation, while some Belgian/saison strains can reach 85-92%. Low attenuation may indicate a stuck fermentation, while very high attenuation can produce a thin, dry beer. Real attenuation is about 82% of apparent attenuation due to alcohol's lower density.

Yes, several formulas exist:
• Standard: ABV = (OG - FG) × 131.25 — most common for homebrewers, accurate within ±0.2% for typical beers.
• Alternate: ABV = (OG - FG) × 133 — slightly higher estimate.
• Daniels Formula: ABV = (76.08 × (OG-FG) / (1.775-OG)) × (FG/0.794) — more accurate for high-gravity beers.
For most homebrew (ABV 3-8%), the standard 131.25 formula is perfectly adequate and widely accepted.

OG: Take a sample of cooled wort (before pitching yeast) using a sanitized hydrometer or refractometer. Ensure the sample is at calibration temperature or apply temperature correction. FG: Take a sample after fermentation activity stops (typically 7-14 days). Wait for stable gravity readings 2-3 days apart before bottling to avoid bottle bombs. For refractometers, use an online refractometer correction calculator since alcohol affects the reading.

The calorie estimate (~30 calories per 12oz per ABV%) is a simplification. Actual calories depend on residual sugars, alcohol content, and other factors. A more precise calculation involves ABW and real extract. For reference: a typical 5% ABV beer has about 150 calories per 12oz, while a 9% imperial stout can exceed 300 calories. Use our estimate as a helpful guideline, not an exact nutritional value.

Yes, but with caution. Refractometers are great for OG readings (only need a few drops) but require correction for FG readings because alcohol changes the refractive index. Use a dedicated refractometer correction calculator for FG. Many brewers use a refractometer for OG and a hydrometer for FG. If using Plato readings from a refractometer, our Plato mode works well for OG but FG Plato values will need external correction.