get FermentCalc

Vinegar Mother Calculator

Enter your liquid volume and its alcohol content, plus how much mother or raw vinegar you have, and get the dilution, the starter share and how long conversion should take.

L

Wine, cider, beer or any other alcoholic liquid you want to convert to vinegar.

%

From the label or a gravity reading. Acetic bacteria work best below about 8%; 6% leaves them headroom.

ml

Live vinegar with the mother, or a vinegar mother itself. More starter means a faster, more reliable start.

Results

Water to add for dilution
1.33L
Total volume after dilution
3.33 L
Starter share
6%
Expected conversion time
4 weeks

Cover the vessel with a cloth so the bacteria breathe but fruit flies stay out, and feed it a splash of alcohol liquid monthly to keep the culture working.

How the vinegar math works

Vinegar fermentation is most reliable below about 8% ABV, so anything stronger is diluted first: the water needed is volume x (ABV - 6) / 6, which lands the batch at 6% alcohol and leaves the bacteria headroom. The starter share is starter milliliters divided by the total milliliters after dilution - roughly 10% or more converts in about 3 weeks, 5-10% in about 4, and under 5% in about 6 at 20-30 C. Finished acidity lands near 5%.

water (L) = V x (ABV - 6) / 6; share = starter / total; weeks = 3, 4 or 6 by share

The ABV calculator turns gravity readings into the alcohol figure this tool needs, and the fermentation time calculator generalizes the temperature adjustment for any ferment.

Frequently asked questions

Do I really have to dilute wine before making vinegar?

Above roughly 8% ABV the acetic bacteria slow down or stall, so strong wine, mead and spirit-based liquids need dilution to about 6% to ferment reliably. Light cider or rice wine at 4-6% can go straight in - the calculator simply adds no water below the target.

Can I use raw store-bought vinegar as starter?

Yes, as long as the label says raw, unfiltered or with the mother. Use at least 10% of the batch volume for a quick start; smaller amounts still work but stretch the timeline. Pasteurized clear vinegar contains no live culture and will not start a ferment.

What is the slimy film in my vinegar?

That is the mother - a cellulose mat of acetic bacteria, and a sign of a healthy culture. Leave it floating or stir it in; only remove it if it grows so thick it blocks air. A cloudy surface is normal, while fuzzy, colored growth means mold and needs removing.