Fun fact
For most of brewing history, fermentation was a lottery. Brewers reused yeast from previous batches without knowing that it was a mix of several species — plus bacteria waiting to sour the beer. In 1883, after years of work at the Carlsberg Laboratory in Copenhagen, Danish physiologist Emil Christian Hansen solved it: he grew yeast cultures from single cells, isolated the best lager strain, and in November 1883 Carlsberg brewed the world's first commercial beer with a pure yeast culture. The strain was named Saccharomyces carlsbergensis (today S. pastorianus). Founder J.C. Jacobsen refused to keep the breakthrough secret and shipped the pure yeast free to breweries worldwide — which is why most lagers on the planet still descend from Hansen's isolate.
Tool usage guide
- Open the Yeast Viability tab, enter the yeast's production date and packaging type — the calculator shows how many viable cells are left.
- Switch to Pitching Rate, enter batch size, gravity (SG or °P) and beer style (ale or lager) to get the billions of cells needed.
- Compare the two numbers: if your pack falls short, use the Yeast Starter tab to plan a starter that grows the missing cells.
- Using dry yeast? Check Dry Rehydration for the right water volume and temperature.
- Pitch at the recommended rate — a healthy ferment starts 12–24 hours sooner and tastes cleaner.