Original Gravity Calculator
Calculate expected original gravity (OG) for your homebrew from grain bill.
Enter grain weight, extract efficiency, and batch size.
How Original Gravity Is Calculated for Homebrew
Original Gravity (OG) measures the sugar content of wort before fermentation. It predicts potential alcohol content and helps you match your recipe to the target beer style.
Extract-Based OG Formula:
OG = 1 + (PPG × Weight_lbs / Volume_gal) / 1000
Where PPG = points per pound per gallon (a measure of fermentable yield):
- Pale 2-row malt: 37 PPG (at ~75% efficiency)
- Crystal/caramel malt: 34 PPG
- Roasted barley: 25 PPG
- Dry malt extract (DME): 45 PPG
- Liquid malt extract (LME): 36 PPG
All-Grain with Mash Efficiency:
OG = 1 + (Grain_lbs × Max_PPG × Efficiency% / Batch_gallons) / 1000
Worked Example: 5-gallon all-grain American Pale Ale, 75% mash efficiency:
- 10 lbs 2-row (max 37 PPG) → contribution = 10 × 37 × 0.75 = 277.5 points
- 0.5 lbs Crystal 40 (max 34 PPG) → contribution = 0.5 × 34 × 0.75 = 12.75 points
- Total gravity points = 290.25 / 5 gallons = 58.05 points
- OG = 1.058
Target OG by Style:
- American Light Lager: 1.028–1.040
- Pale Ale / IPA: 1.044–1.070
- Stout: 1.060–1.090
- Belgian Tripel: 1.075–1.085
- Barleywine: 1.080–1.120
Correcting Low OG: Add DME to raise gravity: each 0.25 lbs DME per gallon raises OG by approximately 9 points (e.g., 1.050 → 1.059).
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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