# How do you calculate the size of a yeast starter?

To calculate the size of a starter, you need to consider the starting gravity and volume of your batch. This calculation will help you determine the total number of yeast cells needed for your batch.

First, it is important to understand that yeast starters are typically expressed in billions of cells. The recommended pitching rate varies depending on the type of you are . For ales, it is generally recommended to pitch 0.75 million cells per milliliter per degree Plato. For lagers, the recommended rate is 1.5 million cells per milliliter per degree Plato, and for hybrids, it is 1.0 million cells per milliliter per degree Plato.

To calculate the size of your yeast starter, you will need to follow these steps:

1. Determine the desired pitching rate for your specific beer style. This information can be found in brewing references or guidelines for the style you are aiming to brew.

2. Measure the starting gravity of your batch using a hydrometer or refractometer. This will give you the degree Plato value.

3. Determine the desired volume of your batch. This is typically measured in liters or gallons.

4. Multiply the desired pitching rate by the volume of your batch and the degree Plato value. This will give you the total number of yeast cells needed for your batch.

For example, let's say you are brewing an with a starting gravity of 1.050 (12.4 degrees Plato) and a batch volume of 20 liters. The recommended pitching rate for ales is 0.75 million cells per milliliter per degree Plato.

1. Pitching rate: 0.75 million cells/mL-P
2. Starting gravity: 1.050 (12.4 degrees Plato)
3. Batch volume: 20 liters

Calculation: 0.75 million cells/mL-P x 20 liters x 12.4 degrees Plato = total number of yeast cells needed for the batch

In this example, the total number of yeast cells needed for the batch would be calculated as follows:

0.75 million cells/mL-P x 20 liters x 12.4 = 186 million yeast cells

Therefore, you would need approximately 186 billion yeast cells for this specific batch.

It is worth mentioning that the pitching rate can vary depending on various factors such as the yeast strain, fermentation conditions, and desired outcome. It is always a good idea to consult brewing references and consider any specific recommendations provided by the yeast manufacturer.

Calculating the size of a yeast starter involves determining the desired pitching rate, measuring the starting gravity and volume of your batch, and multiplying these values together. This calculation will give you an estimate of the total number of yeast cells needed to achieve a healthy fermentation and desired flavor profile for your beer.