Formula Used
Strike water equals grain weight multiplied by mash thickness. Grain displacement adds occupied volume beyond the water itself. Fixed equipment spaces are then added.
Thermal expansion applies to heated liquid volume. Recommended capacity includes the selected safety headspace. The final vessel size rounds upward to an available option.
Strike Water = Grain Weight × Mash Thickness Grain Displacement = Grain Weight × Displacement Factor Expanded Liquid = Heated Liquid × (1 + Thermal Expansion %) Total Mash Volume = Expanded Liquid + Grain Displacement + Dead Space + False-Bottom Space Recommended Capacity = Total Mash Volume ÷ (1 − Headspace %) Fill Percentage = Total Mash Volume ÷ Vessel Capacity × 100 First Runnings = Mash Water − Grain Absorption − Dead Space − Equipment Loss Sparge Water = Target Pre-Boil Volume − First Runnings + Equipment Loss
How to Use
- Select the brewing method and enter the complete grain bill.
- Choose a mash thickness or enter an exact strike-water override.
- Add infusions, mash-out water, dead space, and equipment losses.
- Describe the vessel capacity or calculate it from internal dimensions.
- Set safety headspace, expansion, comparison ratios, and available sizes.
- Calculate, review warnings, then export or save the results.
Example Data
| Input | Example | Purpose |
|---|---|---|
| Grain bill | 6 kg | Defines grain volume and absorption. |
| Mash thickness | 2.7 L/kg | Calculates initial strike water. |
| Dead space | 1 L | Allows for unrecoverable liquid. |
| Headspace | 15% | Reduces overflow and stirring risk. |
| Current tun | 35 L | Checks equipment suitability. |
Typical Brewing Guidance
Many infusion mashes use 2.3 to 3.5 litres per kilogram. Brew-in-a-bag systems often use thinner full-volume mashes. Equipment design can change practical limits.
Grain absorption commonly varies with milling and draining. Headspace helps with stirring, foaming, and temperature additions. Confirm values using your own brew records.
Frequently Asked Questions
What size mash tun do I need?
Choose a tun larger than the expanded mash volume. Add enough headspace for stirring and additions.
Why is grain displacement included?
Wet grain occupies physical space inside the vessel. Ignoring displacement can underestimate required capacity.
What headspace percentage should I use?
Ten to twenty percent suits many systems. Larger additions or vigorous stirring may need more.
Does dead space increase mash tun size?
Yes, retained liquid and false-bottom volume consume usable capacity. Include both when they remain filled.
How does brew-in-a-bag affect capacity?
Full-volume BIAB mashes often need more water inside the mash vessel. Bag handling also benefits from extra headroom.
Can I enter exact strike water?
Yes. The override replaces ratio-based strike water while keeping other calculations active.
How is maximum grain bill estimated?
The calculator divides usable vessel volume by mash water and grain displacement per weight unit.
Why include thermal expansion?
Hot liquor occupies slightly more volume than cool liquor. The allowance reduces unexpected overfilling.
How is sparge water estimated?
Estimated first runnings are subtracted from the target pre-boil volume. Equipment losses are then restored.
Should I trust commercial size rounding?
Use it as a purchasing guide. Confirm internal usable capacity before buying equipment.