Yeast Pitch Rate Calculator
Calculate the correct amount of yeast to pitch for your homebrew.
Based on wort volume, OG, and yeast type.
Avoid under-pitching and off-flavors.
How Yeast Pitch Rate Is Calculated
Pitching the correct amount of yeast is critical for clean fermentation. Under-pitching stresses yeast, producing off-flavors; over-pitching can flatten flavor complexity.
Pitch Rate Formula:
Cells Needed = Pitch Rate × Volume(mL) × Gravity Points
Where Pitch Rate by style:
- Ales: 0.75 million cells/mL/°P
- Lagers: 1.5–2.0 million cells/mL/°P
- High-gravity (OG > 1.075): 1.0–1.25 million cells/mL/°P
Converting OG to Plato: °P ≈ (OG − 1) × 250 (simplified) Example: OG 1.052 → 13°P
Worked Example: American Pale Ale: 20 liters, OG 1.052:
- Volume in mL = 20,000 mL
- Gravity in °P = 13
- Cells needed = 0.75 × 20,000 × 13 = 195 billion cells
Commercial Yeast Packages:
- Wyeast smack pack (fresh): ~100 billion cells
- White Labs vial (fresh): ~100 billion cells
- Dry yeast packet (11g, e.g. US-05): ~200+ billion cells
For 195 billion cells, one dry yeast packet is sufficient. Two liquid packages needed, or make a yeast starter.
Yeast Starter Calculation:
Starter Volume (L) = (Cells Needed − Package Cells) / Growth Factor
Growth factor ≈ 100 billion cells per liter of 1.036 starter wort (on a stir plate).
Cell Viability Decreases with Age: Liquid yeast loses ~20% viability per month after manufacture date. Always check package dates.