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.
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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