Mash pH estimator estimate
Enter your grain bill and your water's residual alkalinity. Get a ballpark mash pH before you brew — then confirm it with a meter on brew day.
This is an estimate, not a measurement. It uses a simplified model1 and can be off by 0.1–0.2 pH or more. Use it to plan adjustments; use a calibrated pH meter to know your actual mash pH.
Why mash pH matters
Mash enzymes work best around pH 5.2–5.6 (measured at room temperature). Pale malts pull the mash toward the high end, dark malts pull it down, and alkaline water pushes it up. Getting close means better conversion, clearer beer, and cleaner flavour.
Notes
- The model treats each malt as a buffer with its own distilled-water mash pH, weights them by mass, then shifts the result by the water's residual alkalinity: pH = Σ(mass × malt pH) ÷ Σmass + RA(meq) ÷ (38 × kg grain). Malt pH comes from colour: base 5.80 − 0.028 × °L, crystal 5.22 − 0.00504 × °L, roast 4.70. These are approximations of published homebrew measurements (Troester; Palmer & Kaminski, Water). Real malts vary by maltster and lot.
- Full water tools such as Bru'n Water and similar spreadsheets use more inputs — per-malt titration data, acid malt and acid additions, mash thickness effects, and more — and still recommend a meter. The roast-malt figure is the weakest part of this model; for grists heavy in dark malt, expect it may read high.
- Residual alkalinity (Kolbach) is alkalinity minus the pH-lowering effect of calcium and magnesium. With ion concentrations in mg/L: RA = alkalinity − Ca/1.40 − Mg/1.70, derived from Kolbach's hardness divisors 3.5 and 7.
- Target range 5.2–5.6 is for a room-temperature sample, which is how most meters are used and how most guidance is written. A sample read hot shows roughly 0.2–0.3 lower; published figures for the offset vary. Always cool the sample before measuring, which also protects the probe.
- Homebrewing beer for personal use is legal federally in the US; check your state and local laws.