Determine the number of yeast cells needed
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This calculator determines the number of yeast cells needed to innoculate wort. There are essentially two approaches. The brewing industry standard is to pitch yeast slurries from previous batches. The second approach is to follow the yeast pitching guidelines provided by the makers of yeast cultures. For both approaches, stronger beers and colder fermentation temperatures (lager beers) require more yeast cells.
The brewing industry pitching rates are calculated as millions of cells per milliliter per degree Plato. The following innoculation rates are from Hyde (2018) and White and Zainasheff (2010) for repitching yeast slurries.
Fresh, healthy yeast can have a pitching rate that is up to 50% lower than the industry recommendations (White and Zainasheff, 2010, p. 122), so the yeast businesses generally recommend a lower pitching rate than the brewing industry standards. There are some slight variations among yeast producers, but this calculator will provide a ballpark figure.
For dry commercial yeast, most yeast companies recommend .5 g to 1.0 g per liter (see Lallemand's catalog). The higher rate of 1.0 g/l is recommended for strong ales. Lager beer pitching rates are about double the ale pitching rates.For wet commercial yeast, the recommendation from Wyeast is for 6 million cells/ml for low gravity ales (gravity less than 1.060 or 15 degrees plato). Stronger ales need 12 million/ml (1.061 to 1.075; 15 to 19 degrees Plato) or 18 million/ml (greater than 1.075 or 19 degrees plato). These rates increase to 12 million/ml, 18 million/ml, and 24 million/ml, respectively for stronger beers, when lager yeast is pitched at cold temperatures.
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