Mash Acid Addition Calculator
Lactic or phosphoric acid needed to cut your water’s alkalinity and bring mash pH down.
Mash + sparge water to treat
mg/L from your water report
mg/L you want to reach
1.5 mL
Acid to addto reduce alkalinity
How it works
The acid required is the milliequivalents of alkalinity you need to neutralise divided by the acid's normality. Alkalinity as CaCO₃ has an equivalent weight of 50, so each 50 mg/L over the treated volume is one milliequivalent per litre.
mEq acid = (ΔAlkalinity as CaCO₃ / 50) × litres
mL = mEq / acid normality
Sources: Bru'n Water - Water Knowledge and Brew Your Own - Residual Alkalinity & pH.
Handle concentrated acids with care and always verify mash pH with a meter.
Frequently asked questions
- Why add acid to brewing water?
- High-alkalinity water resists pH drops and can push mash pH too high, dulling flavour and hop bitterness. Adding food-grade acid neutralises alkalinity so the mash settles into the 5.2–5.6 range.
- Which acid should I use?
- Lactic acid (often 88%) is common and adds a slight tang; phosphoric acid is flavour-neutral, which suits delicate or hoppy beers. Pick the acid you have and match its strength here.
- Is this exact?
- It is an estimate based on neutralising alkalinity as CaCO₃. Always confirm with a calibrated pH meter on the actual mash, since grain bill and water buffering also affect the result.