Yeast Pitching Rate Calculator
Calculate the exact number of yeast cells needed for your homebrew batch.
Understanding Yeast Pitching Rates
Pitching the right amount of yeast is critical for producing clean, professional-quality beer. Under-pitching can lead to sluggish fermentations, off-flavors like diacetyl or acetaldehyde, and higher risks of infection. Over-pitching, while less common for homebrewers, can strip away desired esters and mouthfeel.
The Pitching Formula
The standard formula used by professional brewers is:
Cells Needed = Pitch Rate × Wort Volume (mL) × Degrees Plato
Degrees Plato (°P) is a measurement of the concentration of dissolved solids in the wort. For most brewers using Specific Gravity (SG), we convert it using the formula: °P = (SG – 1.000) / 0.004.
Standard Pitch Rate Guidelines
| Beer Type | Recommended Rate (Million cells/mL/°P) |
|---|---|
| Low Gravity Ales (< 1.040) | 0.35 – 0.50 |
| Standard Ales (1.040 – 1.060) | 0.75 |
| High Gravity Ales (> 1.060) | 1.00 – 1.25 |
| Standard Lagers | 1.50 |
| High Gravity Lagers | 2.00 |
Example Calculation
If you are brewing 20 liters of an Ale at 1.050 (12.5°P) with a target rate of 0.75:
- Convert Volume: 20L = 20,000 mL
- Calculation: 0.75 million × 20,000 mL × 12.5 °P
- Result: 187.5 Billion Cells
- If using 100B cell packs: You would need approximately 1.88 packs (or a yeast starter).
Why Pitch Rates Vary?
Lagers require higher pitching rates because they are fermented at colder temperatures. Yeast metabolism is slower in the cold, so more "workers" are needed to ensure the fermentation starts promptly and finishes completely. Similarly, high-gravity beers (high sugar content) put more osmotic stress on yeast cells, requiring a higher cell count to handle the workload.