# Yeast Calculator

The Yeast Calculator determines optimal yeast amounts and calculates starter requirements for liquid yeast.

![Calculate how many yeast packages to add or how big of a starter to make](https://771697612-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LEzhWP2LGeXaKgS2qr4%2F-LFRyl_P6JbL2o6antht%2F-LFRz7vV7GrzRxnwYWEd%2Fimage.png?alt=media\&token=3290722d-2721-4f7b-9213-16ae612c7601)

## How to Use

The tool is divided into two sections: **Pitch Rate** (top) and **Yeast Starter** (bottom).

### Pitch Rate Section

| Input                | Description                                                                                |
| -------------------- | ------------------------------------------------------------------------------------------ |
| **Original Gravity** | The target OG of your wort                                                                 |
| **Volume**           | Post-boil volume into the fermenter                                                        |
| **Pitch Rate**       | Select a preset or use the slider to set a custom rate (million cells / ml / degree Plato) |
| **Yeast Form**       | Choose between Dry or Liquid yeast                                                         |

#### Pitch Rate Presets

The pitch rate selector offers these presets:

* **0.35** -- Minimum
* **0.75** -- Ale up to 1.060
* **1.00** -- Ale 1.060 or more
* **1.50** -- Lager up to 1.060
* **2.00** -- Lager 1.060 or more

A slider allows fine-tuning the pitch rate from 0.35 to 2.50.

#### Dry Yeast Inputs

When Dry is selected, these additional inputs appear:

| Input                      | Description                                                  |
| -------------------------- | ------------------------------------------------------------ |
| **grams per pkg**          | Weight of yeast per package (default 11.5)                   |
| **Billion cells per gram** | Cell density of the dry yeast (default 13)                   |
| **Rehydrate**              | Checkbox to indicate whether you plan to rehydrate the yeast |

#### Liquid Yeast Inputs

When Liquid is selected, these additional inputs appear:

| Input                     | Description                                                                                      |
| ------------------------- | ------------------------------------------------------------------------------------------------ |
| **Billion cells per pkg** | Cell count per liquid yeast package (default 100)                                                |
| **Calc viability**        | Checkbox to automatically calculate viability from the manufacturing date                        |
| **PurePitch**             | Checkbox for White Labs PurePitch packets (uses a different viability curve)                     |
| **Manufacturing date**    | The yeast package manufacturing date                                                             |
| **Viability**             | Percentage of viable cells (auto-calculated when "Calc viability" is checked, or enter manually) |

#### Pitch Rate Output

The output card shows:

* **Target pitch** -- the total billion cells needed
* **Yeast to use** -- number of packages needed (rounded up), with the fractional value shown for reference
* **Billion cells total** -- the actual cell count from the recommended number of packages
* **Target diff** -- how many billion cells above or below target

### Yeast Starter Section

The starter section calculates how large a starter you need to grow enough cells.

| Input                    | Description                                                                                                         |
| ------------------------ | ------------------------------------------------------------------------------------------------------------------- |
| **Start amount**         | Number of packages or billion cells to begin the starter with (toggle between "Packages" and "Billion cells" modes) |
| **Overbuild**            | Extra billion cells to grow beyond your pitch target, for harvesting and saving for future brews                    |
| **Growth Model Formula** | Choose between **No Stir (Chris White)** or **Stir (Braukaiser)**                                                   |
| **Calc starter size**    | Checkbox to let the tool automatically calculate the optimal starter volume                                         |

#### Multi-Step Starters

The tool supports **up to 10 starter steps**. Use the **Add step** and **Remove step** buttons to manage steps. Each step has:

| Input       | Description                                                                                             |
| ----------- | ------------------------------------------------------------------------------------------------------- |
| **Gravity** | The gravity of the starter wort for that step (editable when using the Braukaiser model; default 1.036) |
| **Size**    | The volume of the starter step (auto-calculated when "Calc starter size" is checked, or enter manually) |

#### Per-Step Output

Each step displays a result card showing:

* **Step number** (when multiple steps are present)
* **Starter volume** and required **DME amount**
* **New count** -- the total billion cells after this step (color-coded: green when target is met, yellow when close, red when insufficient)
* **Difference vs target pitch rate** in billion cells
* **Pitch Rate** -- million cells / ml achieved
* **Inoculation Rate** -- million cells / ml (ideally between 25 and 100 for best growth)
* **Growth Factor** -- ideally at least 1.0

When **Overbuild** is set, each step additionally shows:

* **Overbuild Harvest** -- the volume and percentage of the starter to harvest and save
* **Pitch Amount** -- the volume to pitch into your wort

Each step also shows the **Liquid Malt Extract** equivalent alongside the DME amount.

## Recommended Pitch Rates

### By Beer Type

* **Ales**: 0.75 million cells/ml/°P (standard)
* **Lagers**: 1.5 million cells/ml/°P (double ale rate)
* **High Gravity** (>1.065): 1.0-1.25 million cells/ml/°P
* **Belgian/Wheat**: 0.5-0.75 million cells/ml/°P

### Factors Affecting Pitch Rate

* **Wort Gravity**: Higher gravity needs more yeast
* **Beer Style**: Lagers need more than ales
* **Yeast Health**: Older yeast needs higher pitch rate
* **Fermentation Temperature**: Lower temps need more yeast

## Yeast Viability

### Liquid Yeast Degradation

Yeast viability decreases over time:

* **1 month**: 80-90% viable
* **2 months**: 60-75% viable
* **3 months**: 40-60% viable
* **4+ months**: Consider a starter

### PurePitch® Viability

Formula for White Labs PurePitch® packets:

| Time     | Viability |
| -------- | --------- |
| 1 month  | 99.21%    |
| 2 months | 98.05%    |
| 3 months | 90.26%    |
| 4 months | 84.28%    |
| 5 months | 79.35%    |
| 6 months | 71.59%    |

### Dry Yeast

* Longer shelf life than liquid
* 2 years typical viability
* 10-20 billion cells/gram
* No starter needed usually

## Making a Yeast Starter

### Equipment Needed

* **Flask**: 2L or larger Erlenmeyer
* **Stir Plate**: Optimal for growth
* **Stir Bar**: Magnetic, sanitized
* **DME**: Dry malt extract
* **Foil**: To cover flask

### Starter Preparation

1. **Calculate DME Amount**
   * 10:1 ratio (100g DME per liter)
   * Target 1.036-1.040 gravity
2. **Boil and Cool**
   * Boil water and DME 10 minutes
   * Cool to room temperature
   * Transfer to sanitized flask
3. **Pitch Yeast**
   * Add yeast to cooled wort
   * Cover with sanitized foil
   * Start stir plate
4. **Growth Phase**
   * 24-48 hours typical
   * Keep at room temperature
   * Constant stirring best

### Stepping Up Starters

For very high cell counts, use the multi-step feature in the tool (up to 10 steps):

1. Make an initial starter (the tool calculates the optimal size)
2. After 24-48 hours, decant and step up to the next volume
3. Each subsequent step typically doubles the previous volume
4. The tool tracks the cumulative cell count through all steps

### Decanting vs. Pitching All

**Decanting** (Recommended for lagers):

* Refrigerate starter overnight
* Pour off clear liquid
* Pitch concentrated yeast

**Pitch Everything** (Common for ales):

* Add entire starter to wort
* Accounts for volume in recipe
* Simpler process

## Pitch Rate Guidelines

### Underpitching Effects

* Longer lag time
* Stressed yeast
* Off-flavors (esters, phenols)
* Incomplete fermentation
* Diacetyl production

### Overpitching Effects

* Less yeast character
* Reduced esters
* Faster fermentation
* Possible autolysis
* Generally less problematic

### Style Considerations

**Clean Beers** (Lagers, Light Ales):

* Higher pitch rates
* Minimize yeast stress
* Clean fermentation

**Character Beers** (Belgian, Hefe):

* Lower pitch rates acceptable
* Encourage ester production
* More yeast expression

## Dry Yeast Guidelines

### Rehydration (Optional)

1. Boil water, cool to 35-40°C (95-105°F)
2. Sprinkle yeast on surface
3. Wait 15 minutes
4. Gently stir
5. Pitch when within 5°C (10°F) of wort

### Direct Pitch

* Modern dry yeast works well
* Sprinkle on wort surface
* No need to rehydrate
* Follow manufacturer guidelines

### Amount Needed

* **Typical**: 1 packet per 19 liters (5 gallons) up to 1.060
* **High Gravity**: 2+ packets
* **Lagers**: Double the ale amount

## Troubleshooting

### Slow Start

* Check viability calculation
* Verify pitch rate
* Consider temperature
* Oxygenation levels

### Stuck Fermentation

* Likely underpitched
* Add fresh yeast
* Make small starter first
* Check temperature

### Off-Flavors

* Review pitch rate
* Check yeast age
* Verify storage conditions
* Consider yeast health

## Using with Your Recipes

* Calculate pitch rates based on your recipe's OG and volume
* The tool remembers your last settings
* Use results to plan yeast purchases and starters
* Track what pitch rates work best for your system

## Tips

* Always calculate pitch rates, don't guess
* Use fresh yeast when possible
* Keep yeast refrigerated
* Aerate wort well before pitching

## Related docs

* [Recipe Designer](https://docs.brewfather.app/recipes/designer)
* [Brewing Knowledge: Fermentation](https://docs.brewfather.app/brewing-knowledge/fermentation)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.brewfather.app/tools/yeast-calculator.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.