# 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)