Tools in This Collection
ABV Calculator
Calculate alcohol by volume from OG and FG
Priming Sugar Calculator
Calculate priming sugar for bottle carbonation
Keg Carbonation Calculator
Set CO2 pressure for target carbonation level
Yeast Starter Calculator
Calculate starter size for target pitch rate
Gravity Converter
Convert between SG, Plato, and Brix scales
Hydrometer Temperature Correction
Correct gravity readings for sample temperature
Mead Calculator
Calculate honey, water, and nutrient additions for mead
Vinegar Dilution Calculator
Dilute vinegar to target acidity percentage
The Fermentation Phase: Tracking What Happens After Brewing
After brewday, fermentation management comes down to three measurements: original gravity, final gravity, and temperature. Original gravity (OG) at the start of fermentation, final gravity (FG) after fermentation completes, and the difference between them tells you ABV. The ABV Calculator handles this: OG 1.060 fermented to FG 1.012 gives 6.3% ABV using the standard formula (ABV = 131.25 × (OG - FG)). For high-gravity beers above 1.070 OG, use the more accurate alternate formula available in the calculator.
Gravity Conversions and Hydrometer Correction
Different recipes and hydrometers use different scales: specific gravity (1.050), Plato (12.4°P), and Brix (12.4). The Gravity Converter switches between all three — useful when your brewing software outputs in Plato but your hydrometer reads in SG. Temperature matters for accuracy: hydrometers are typically calibrated at 60°F (15.6°C). Measuring a 90°F wort directly gives a falsely low reading. The Hydrometer Temperature Correction Calculator adjusts your reading to the calibration temperature automatically.
Bottle Carbonation and Keg Carbonation
Bottle carbonation with priming sugar requires precise calculation. Too little sugar: flat beer. Too much: over-carbonated or bottle bombs. Target carbonation levels by style: most ales at 2.4-2.8 volumes CO2, German hefeweizen at 3.5-4.5 volumes, Belgian tripel at 3.0-4.0 volumes, English cask ales at 1.0-1.5 volumes. The Priming Sugar Calculator accounts for residual CO2 from fermentation temperature (beer fermented at 68°F retains about 0.85 volumes; at 62°F it retains about 1.04 volumes) and calculates the exact sugar addition for any target CO2 volume. For kegging, the Keg Carbonation Calculator shows the serving pressure and temperature needed to maintain your target carbonation — typically 10-12 PSI at 38°F for 2.5 volumes.
Yeast Pitching, Mead, and Vinegar
Proper yeast pitch rate prevents under-fermentation, off-flavors, and stuck fermentation. Standard recommendation: 0.75 million cells per mL per degree Plato for ales, 1.5 million for lagers. A 5-gallon batch of 1.060 OG ale (14.7°P) needs approximately 189 billion yeast cells — one pack of liquid yeast contains about 100 billion viable cells, so a starter is often needed. The Yeast Starter Calculator recommends starter size and gravity to reach your target cell count. Mead brewers can use the Mead Calculator to estimate potential ABV from honey additions and batch size — 1 lb of honey per gallon contributes approximately 1.035-1.040 points to OG. The Vinegar Dilution Calculator helps calculate how much water to add to mother vinegar to hit a target acidity percentage for cooking or preservation.
Frequently Asked Questions
How do I calculate ABV from original and final gravity?
Standard formula: ABV = 131.25 × (OG - FG). Example: OG 1.060, FG 1.012 → ABV = 131.25 × (1.060 - 1.012) = 131.25 × 0.048 = 6.3%. For high-gravity beers (OG above 1.070), use the more accurate alternate formula: ABV = (76.08 × (OG - FG) / (1.775 - OG)) × (FG / 0.794). The difference is small at typical gravity ranges but meaningful for barleywines and imperial stouts.
How much priming sugar do I use for bottle carbonation?
Priming sugar amount depends on your target CO2 volume and the temperature at which fermentation finished (which determines residual CO2). For a standard American pale ale targeting 2.5 volumes CO2 in a 5-gallon batch fermented at 68°F: approximately 3.5-4 oz (100-115g) of corn sugar. Use the Priming Sugar Calculator with your exact batch size, target CO2, and fermentation temperature for a precise addition. Always dissolve sugar in boiled water before adding to the beer.
What CO2 volume should I target for different beer styles?
CO2 volume targets by style: American ales 2.4-2.8, English cask ales 1.0-1.5, German hefeweizen 3.5-4.5, Belgian saison 2.5-3.5, Belgian tripel 3.0-4.0, American lager 2.5-3.0, German Pilsner 2.5-3.0. Higher carbonation makes beer feel crisper and more effervescent; lower carbonation makes it feel rounder and maltier. Hefeweizens are intentionally very highly carbonated to lift the yeast in suspension.
How do I know if I need a yeast starter?
Use a starter when your batch gravity is above 1.060 OG, when using liquid yeast older than 4 weeks from manufacture date, or when pitching into a cold environment. A standard 5-gallon 1.050 OG ale needs about 150-200 billion cells — one pack of fresh liquid yeast (100 billion viable) is borderline. Above 1.065 OG, a starter is generally recommended. Dry yeast (typically higher cell counts) usually doesn't require a starter for standard-gravity beers.