Mash pH & Water Chemistry Calculator
Build your brewing water: salt additions, ion levels, residual alkalinity, estimated mash pH and the sulfate-to-chloride balance - free, no spreadsheet, no login.
1 · Your water & batch
2 · Source water profile (mg/L)
From your water report, or 0 across the board if brewing with distilled/RO.
3 · Brewing salt additions (grams)
Resulting water (mg/L)
How it works
Each brewing salt dissolves into known ion contributions. We add those to your source water, then compute residual alkalinity (Kolbach) and estimate how far it shifts mash pH from the distilled-water baseline of your grist. The sulfate-to-chloride ratio summarises the flavour lean.
RA = Alkalinity(as CaCO₃) − (Ca/3.5 + Mg/7)
mash pH ≈ base pH + RA × coefficient
Sources: residual alkalinity after Kolbach (1953); mash-pH and water chemistry per Palmer, How to Brew ch.15 and Kai Troester (Braukaiser).
Which pH model?
The RA-to-pH coefficient has two published values, and we let you pick:
- Kolbach (classic) - 0.00168 pH per ppm of RA (0.3 pH per 10 °dH). The textbook value from Kolbach's 1953 paper, reproduced in Brew Your Own. It assumes an idealised 100% response, so it tends to overstate how far your water moves the pH.
- Empirical (Troester) - about 0.00097, ~60% of Kolbach. Kai Troester's mash experiments found real grists buffer the swing, so this is usually closer to what your pH meter will read.
Either way this is a planning estimate - it models only the water side, not your specific malts' acidity (that's what a full grain-bill tool like Bru'n Water adds). The true value depends on your whole grist; always confirm with a calibrated pH meter on a cooled sample, then adjust.
Frequently asked questions
- What is residual alkalinity and why does it matter?
- Residual alkalinity (RA) is the part of your water's alkalinity that calcium and magnesium do not offset. High RA pushes mash pH up; low or negative RA pulls it down. It is the single most useful number for predicting how your water will behave in the mash. We use the Kolbach formula: RA = alkalinity (as CaCO₃) − (Ca/3.5 + Mg/7).
- What mash pH should I aim for?
- A room-temperature mash pH of roughly 5.2–5.6 is the usual target for most beers. Lower within that band suits pale, hop-forward beers; higher suits darker, malt-forward beers. This tool estimates where you will land and lets you adjust salts and acid to hit it.
- What is the sulfate-to-chloride ratio?
- It is a flavour-balance lever. More sulfate accentuates hop bitterness and dryness; more chloride accentuates malt fullness and sweetness. A ratio near 1 is balanced; 2:1 or higher leans hoppy; below 1 leans malty. It is a guide, not a rule.
- Do I need Bru'n Water or a spreadsheet for this?
- No. This calculator does the same core water chemistry - ion contributions from brewing salts, residual alkalinity, estimated mash pH and the sulfate-to-chloride balance - in your browser, free, with nothing to download.