Build Your Grain Bill
Enter each grain with its weight, points-per-gallon (PPG), and SRM color value.
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An all-grain homebrew calculator determines OG, FG, ABV, IBUs (Tinseth), SRM color (Morey), and all water volumes for brew day. Enter your grain bill with mash efficiency and hop schedule with boil times to get every number you need before firing up the kettle.
Recipe Settings
Grain Bill
Hop Schedule
Recipe Results
OG—
FG—
ABV—
IBU—
SRM—
BU:GU—
Beer Color
Water Volumes
Mash Water—
Sparge Water—
Pre-Boil Volume—
Total Water—
How It Works
Add Your Hops
Enter each hop addition with weight, alpha acid percentage, and boil time.
Get Every Number
OG, FG, ABV, IBU (Tinseth), SRM (Morey), BU:GU ratio, and all water volumes.
Water Volumes
Mash water (1.25 qt/lb), sparge water, pre-boil volume — ready for brew day.
Why ABV and IBU Math Matters
Brewing is chemistry. Your OG (Original Gravity) predicts how much sugar your yeast can convert to alcohol, and IBU (International Bitterness Units) tell you how bitter the beer will taste. Getting these numbers right before brew day means no surprises — your pale ale won't turn into a barleywine. BrewMath uses the Tinseth IBU formula (the industry standard for utilization curves) and Morey SRM color (MCU → SRM). Every calculation runs in your browser.
Frequently Asked Questions
How do you calculate ABV for homebrew beer?
ABV = (Original Gravity - Final Gravity) × 131.25. Measure Original Gravity (OG) with a hydrometer before pitching yeast, and Final Gravity (FG) after fermentation completes. For example: OG 1.050 - FG 1.010 = 0.040 × 131.25 = 5.25% ABV.
What is IBU and how is it calculated for homebrew?
International Bitterness Units (IBU) measure hop bitterness in beer. The Tinseth formula calculates IBU from hop weight, alpha acid percentage, boil time, and wort gravity: IBU = (Weight in oz × Alpha Acid % × Utilization × 74.9) / Volume in gallons. Utilization is scored at the average gravity of the wort during the boil, the mean of pre-boil and post-boil gravity, not the OG shown in the results panel. Longer boil times and lower gravity increase hop utilization and bitterness.
How much water do I need for all-grain brewing?
Total water = Mash water (1.25-1.5 quarts per pound of grain; this calculator uses 1.25) + Sparge water (enough to reach pre-boil volume) + Boil-off (typically 1-1.5 gallons per hour) + Grain absorption (0.5 quarts, or 0.125 gallons, per pound) + Equipment dead space. For a 5-gallon batch with 10 lbs grain this calculator returns 7.3 gallons of mash plus sparge water; add your own kettle dead space, trub and chiller losses on top.