Yeast pitch rate calculator
Underpitching stresses yeast and can bring off-flavors; overpitching wastes it. Enter the batch size and original gravity and choose ale or lager. The calculator gives the cells needed with the common pitch rates and translates them into liquid packs and dry yeast, with the cell counts you set.
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How to use
- Choose the beer type, which sets the pitch rate.
- Choose liters or US gallons and enter the wort volume going into the fermenter.
- Enter the original gravity.
- Check the cell counts for your liquid packs and dry yeast and change them if your supplier gives other numbers.
- Read the cells needed and how many packs, grams or sachets that is.
How it works
Cells in billions = rate × liters × °P, because rate (million per mL per °P) × 1000 mL per liter ÷ 1000 million per billion = 1. Liquid packs = cells ÷ (cells per pack × viability). Dry yeast grams = cells ÷ cells per gram, sachets = grams ÷ sachet weight. Gallons are converted with 1 US gal = 3.785 L.
Example
5 gallons of ale at 1.050:
- 5 gal = 18.93 L, and 1.050 = 12.39 °P;
- cells: 0.75 × 18.93 × 12.39 = 176 billion;
- liquid packs of 100 billion at full viability: 176 ÷ 100 = 1.8, so two packs or a starter;
- dry yeast at 10 billion per gram: 17.6 g, which is 1.5 sachets of 11.5 g.
Tips
- Round up rather than down: a little extra yeast is safer than too little.
- Rehydrating dry yeast in warm water before pitching is what many makers recommend; check the instructions on the sachet.
- High-gravity beers above about 1.070 benefit from the strong-ale or strong-lager rates and good aeration.
Frequently asked questions
What pitch rate should I use?
Common rates are 0.75 million cells per milliliter per degree Plato for ales, about 1.0 for strong ales, 1.5 for lagers and 2.0 for strong lagers. Lagers need more because they ferment cold, where yeast grows slowly.
How many cells are in a pack of liquid yeast or a gram of dry yeast?
That depends on the product and its age, so the calculator lets you set both. A fresh liquid pack is often quoted at around 100 billion cells and loses viability as it ages; dry yeast is commonly estimated at 10 to 20 billion cells per gram. Use the numbers your supplier gives and lower the viability for older packs.
What if I need more than one pack?
Either pitch several packs or grow a yeast starter a day or two before brewing. With a starter, enter the cells the starter produced as the pack size and one pack.
Why is gravity in degrees Plato?
Pitch rates are given per degree Plato, the sugar content as percent by weight. The calculator converts specific gravity with °P = −616.868 + 1111.14 SG − 630.272 SG² + 135.997 SG³, so 1.050 is about 12.4 °P.