Calculate how many yeast cells or packets you need for a healthy fermentation based on batch size, gravity, and beer type.
Proper yeast pitch rate is critical for clean fermentation. Under-pitching leads to off-flavors, stalled fermentation, and stressed yeast. Over-pitching can reduce ester production (sometimes desirable).
Gravity to Plato conversion: °P = −676.0720 + 1286.4851 × SG − 800.5033 × SG² + 190.0859 × SG³
Yeast cell counts: A standard liquid yeast pack (White Labs / Wyeast) contains ~100 billion viable cells when fresh. A standard 11.5g dry yeast sachet contains ~230 billion cells.
Tip: For high-gravity beers (>1.070), consider making a yeast starter to increase cell count without buying many packs.