Enter Mash and Sparge Details
Formula Used
Mash water: grain weight × mash thickness
Grain absorption: grain weight × absorption rate
First runnings: mash water − grain absorption − mash tun dead space
Boil-off: boil-off rate × boil time in hours
Hot post-boil volume: (target fermenter volume + kettle loss) ÷ (1 − shrinkage)
Pre-boil volume: hot post-boil volume + boil-off
Sparge water: pre-boil volume − first runnings
Strike temperature: target mash temperature + (0.41 ÷ mash ratio qt/lb) × (target mash temperature − grain temperature)
Estimated OG: 1 + [(grain lb × PPG × efficiency) ÷ target gallons] ÷ 1000
How to Use This Calculator
Enter the grain bill weight first. Then add your target fermenter volume. Choose liters or gallons for your batch measurements. Set mash thickness based on your normal process. Add grain absorption, mash tun dead space, boil time, boil-off rate, kettle loss, and cooling shrinkage. Enter your target mash temperature and grain temperature. Add your expected brewhouse efficiency and average grain potential. Press the calculate button. The results appear above the form and below the header. Use the CSV button for spreadsheet records. Use the PDF button for brew day notes.
Example Data Table
| Batch Style | Grain Weight | Target Volume | Mash Thickness | Boil Time | Expected Result |
|---|---|---|---|---|---|
| Small pale ale | 4.50 kg | 18 L | 3.0 L/kg | 60 min | Balanced mash with moderate sparge need |
| Standard ale | 5.00 kg | 20 L | 3.0 L/kg | 60 min | Common home batch water plan |
| Strong wort | 7.20 kg | 20 L | 2.7 L/kg | 75 min | Higher mash water and higher gravity |
| Large kettle batch | 8.00 kg | 30 L | 3.2 L/kg | 90 min | Greater total water and boil-off allowance |
Mash and Sparge Planning Guide
Why Water Planning Matters
A good brew day starts with a clear water plan. Mash water hydrates the crushed grain. It also sets the mash thickness. Sparge water rinses sugars from the grain bed. Both values affect kettle volume, gravity, and process control. Small errors can create a thin wort, low volume, or missed gravity target.
Mash Thickness and First Runnings
Mash thickness shows how much water meets each kilogram of grain. A thinner mash may stir more easily. A thicker mash may fit smaller vessels. The calculator multiplies grain weight by mash thickness. It then subtracts grain absorption and mash dead space. That gives estimated first runnings. This value helps you see how much wort may leave the mash before sparging.
Sparge Volume and Kettle Target
The sparge amount depends on the pre-boil target. The tool builds that target from fermenter volume, kettle loss, cooling shrinkage, boil time, and boil-off rate. This approach is more useful than guessing sparge water alone. It connects the mash plan to the final volume you want after chilling and transfer.
Strike Heat and Gravity Estimate
Strike temperature is the hot water temperature before grain is added. Cool grain absorbs heat. A thicker mash also changes the heat balance. The calculator uses the common infusion equation with the mash ratio converted to quarts per pound. It also estimates gravity from grain potential and efficiency. This is an estimate, not a lab reading. Actual results depend on crush, pH, recirculation, lautering, and measurement accuracy.
Using the Results
Use the mash water result for your first water addition. Use the sparge result for your rinse water. Check total water before heating. Compare pre-boil gravity with your hydrometer or refractometer reading. Record the CSV or PDF output after each batch. Over time, adjust absorption, boil-off, and efficiency values to match your own equipment.
FAQs
1. What does mash water mean?
Mash water is the hot water mixed with crushed grain. It hydrates the grain and creates the mash thickness used during conversion.
2. What does sparge water mean?
Sparge water is rinse water added after mashing. It helps collect more sugars and reach the required pre-boil kettle volume.
3. Why is grain absorption important?
Grain holds water after draining. Ignoring absorption can make the pre-boil volume too low and change the final batch size.
4. What is mash tun dead space?
Dead space is liquid left behind in the mash tun. It may sit below the outlet or remain trapped in the vessel.
5. Why does boil-off rate affect sparge volume?
Longer or stronger boiling removes more water. The calculator adds that expected loss to the required pre-boil volume.
6. What is cooling shrinkage?
Hot wort contracts when it cools. A shrinkage allowance helps estimate the hot post-boil volume needed for the cold target volume.
7. Is estimated OG exact?
No. It is an estimate based on grain potential and efficiency. Real readings depend on crush, mixing, pH, losses, and measurement tools.
8. Can I use gallons?
Yes. Choose gallons as the volume unit. Grain weight and mash thickness still use kilograms and liters per kilogram for consistency.