Vinegar Mother Calculator

The calculator applies a fixed targetAceticPct = startingABV * 0.95 regardless of temperature, mother size, or vessel volume — those other inputs only affect how many days the conversion takes, not the final acid yield. This models the fact that even a complete, well-run conversion loses some ethanol to evaporation and incomplete oxidation rather than converting perfectly 1:1 to acetic acid.

This looks counterintuitive but it's a quirk of the tiered temperature factor: 77–86°F gets the fastest factor of 0.8, but 70–76°F is also treated as merely acceptable at factor 1.0 — so 72°F and 80°F actually land in different tiers with 80°F genuinely faster (0.8 vs 1.0), not slower. If you're seeing the opposite, double check which side of the 77°F threshold your entered temperature falls on, since the calculator uses hard cutoffs rather than a smooth curve.

The calculator computes motherRatio as mother weight divided by vessel volume, then applies a factor of 0.7 at ratios of 10% or higher, 1.0 between 5–10%, and 1.4 below 5%. A larger starting culture means more active acetobacter biomass already present relative to the batch size, so there's simply more bacteria working to convert the ethanol from day one, which is why the model rewards a higher mother-to-volume ratio with a shorter timeline.

The chart is generated by linearly interpolating from 0% up to the target acetic acid percentage across the estimated number of days, using simple proportional steps rather than any biological growth curve. Real vinegar fermentation typically has a slower initial lag phase followed by faster conversion once the acetobacter colony is established, so treat this chart as a rough timeline guide rather than a prediction of the actual day-to-day acid curve.