> For the complete documentation index, see [llms.txt](https://docs.brewfather.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.brewfather.app/tools/mash-tun-calibration.md).

# Mash-Tun Calibration

Determines your mash tun's heat retention characteristics for accurate strike temperature calculations.

## How to Calibrate

1. **Measure your ambient mash-tun temperature** -- the temperature of your empty, dry mash tun
2. **Prepare a carefully measured volume of hot water** and measure its temperature (this is the 0-minute reading)
3. **Add the hot water to the mash tun**, put the lid on, and take a new temperature reading after 5 minutes

### Inputs

The tool has four input fields:

| Input                            | Description                                                                      |
| -------------------------------- | -------------------------------------------------------------------------------- |
| **Mash-Tun Temperature**         | The ambient temperature of your empty mash tun before adding water               |
| **Hot Water Volume**             | The carefully measured volume of hot water you are adding                        |
| **Water Temperature, 0 minutes** | The temperature of the hot water just before you pour it in                      |
| **Water Temperature, 5 minutes** | The temperature of the water inside the mash tun after 5 minutes with the lid on |

### Output

The tool calculates your **Mash-Tun Heat Capacity** expressed in **L equivalent water volume**. Enter this value in your equipment profile to get more accurate strike water temperature calculations.

Higher Mash-Tun Heat Capacity means Brewfather assumes the tun absorbs more heat before the mash reaches its target temperature, so strike water calculations become hotter. Lower values make the calculated strike temperature lower.

## Why Calibrate

Every mash tun loses heat differently based on:

* **Material**: Plastic, stainless steel, copper
* **Insulation**: Quality and thickness
* **Size**: Surface area to volume ratio
* **Environment**: Ambient temperature
* **Preheating**: How well you preheat

Calibration gives you a Mash-Tun Heat Capacity value specific to your equipment.

## Understanding the Results

### Mash-Tun Heat Capacity Values

* **0.0**: Perfectly preheated, no heat loss to the mash tun
* **0.1-0.2**: Well insulated or preheated
* **0.2-0.3**: Average homebrew setup
* **0.3-0.5**: Poor insulation or cold tun

### Using Your Result

* Enter the value in your equipment profile
* Use with the Strike Temperature Calculator for accurate predictions
* Consistent mash temperatures
* Better enzyme activity

### If Your Mash Misses Target

First verify the measured inputs: grain temperature, empty mash-tun temperature, mash water volume, water temperature, and thermometer accuracy.

* **Actual mash too high**: the calculated strike temperature was too high for your process. Recalibrate and use a lower Mash-Tun Heat Capacity, or preheat the tun consistently and use a value close to 0.
* **Actual mash too low**: the calculated strike temperature was too low for your process. Recalibrate and use a higher Mash-Tun Heat Capacity if the tun is absorbing more heat than modeled.
* Avoid changing the value in the wrong direction as a manual offset. Increasing Mash-Tun Heat Capacity raises the strike temperature; decreasing it lowers the strike temperature.

## Improving Heat Retention

### Insulation Options

* **Reflective Bubble Wrap**: Cheap, effective
* **Foam Board**: Cut to fit
* **Sleeping Bag/Blankets**: Simple solution
* **Spray Foam**: Permanent option

### Preheating Methods

1. Fill with hot water 10 min before
2. Rinse with boiling water
3. Heat with strike water overage
4. Store in warm location

## Testing Variables

### What Affects Calibration

* **Ambient Temperature**: Test in brew conditions
* **Wind/Drafts**: Increase heat loss
* **Lid Seal**: Critical for retention
* **Mash Volume**: Fuller tun retains better

### When to Recalibrate

* New equipment
* Changed insulation
* Different season/location
* Inconsistent results

## Practical Examples

### Example 1: Cooler Mash Tun

* 38 liter (10 gallon) cooler
* No preheating
* 21°C (70°F) mash-tun temperature
* Result: 0.25 L equivalent water volume

### Example 2: Insulated Kettle

* Stainless kettle
* Wrapped insulation
* Preheated
* Result: 0.10 L equivalent water volume

## Using Your Calibration

### With Strike Calculator

* Enter the Mash-Tun Heat Capacity value in the Strike Temperature Calculator
* Set it to 0 if your mash tun is pre-heated
* More accurate temperature predictions
* Reduces mash temperature misses
* Recalibrate instead of using arbitrary strike temperature offsets

### With Rest Temperature Calculator

* The same Mash-Tun Heat Capacity value is used when calculating infusion water additions for step mashing

## Tips

* Use consistent test methods
* Calibrate thermometer first
* Test in typical brewing conditions
* Average multiple test results

## Related docs

* [Equipment Profiles](/profiles/equipment.md)
* [Setting Up Your Equipment Profile](/getting-started/setting-up-your-equipment-profile.md)


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