Yeast Pitch Rate Calculator

A pitch rate is the number of yeast cells added per milliliter of wort per degree Plato of gravity. It is expressed in millions of cells/mL/°P. Standard rates are 0.75 M/mL/°P for ales and 1.5 M/mL/°P for lagers, ensuring healthy, complete fermentation.

Under-pitching means adding too few yeast cells for the volume and gravity of your wort. This can lead to stuck or sluggish fermentation, extended lag times, and off-flavors such as excess fusel alcohols or esters. Always target the recommended pitch rate for your beer style.

Yes. Over-pitching is less common but can suppress ester production, leading to a flatter flavor profile — especially noticeable in styles where fruity esters are desirable. It can also cause yeast to skip important growth phases. For most homebrewers, over-pitching is a minor concern compared to under-pitching.

Lagers ferment at colder temperatures (around 48–55°F / 9–13°C), which slows yeast metabolism significantly. A higher pitch rate — typically 1.5 to 2.0 M/mL/°P — compensates for slower cell activity, reducing the risk of off-flavors and ensuring complete attenuation.

Liquid yeast viability decreases approximately 1% per day after the production (manufacturing) date. A fresh pack at 100 billion cells pitched 60 days later retains roughly 40 billion viable cells. This calculator adjusts viability based on the age you enter, so you know how many packs or what starter size you truly need.

A common approximation is °P ≈ (SG − 1) × 250. For example, a wort at 1.050 SG equals roughly 12.5°P. This calculator performs that conversion automatically when you enter your original gravity.

A starter is recommended whenever your liquid yeast pack does not contain enough viable cells to reach the target pitch rate. This is common for beers over 1.040 OG, older yeast packs, or high-gravity brews. A starter in 1–2L of 1.040 DME solution can double or triple your cell count before pitching.

A standard 11g dry yeast sachet (such as Safale US-05) typically contains around 200 billion cells with very high viability since it is dried and packaged. A typical liquid yeast pack (such as Wyeast or White Labs) contains approximately 100 billion cells when fresh, declining over time.