Mead ABV Calculator

Honey must is the one starting liquid where the refractometer and the hydrometer disagree before fermentation even starts. Honey contains 2 to 4 percent non-sugar solids, and honey must is often read above 25 Brix where the ICUMSA Brix to gravity conversion is already stretching. Take the OG on a hydrometer if you can, and if you use the refractometer for the OG, expect it to run slightly high. After fermentation the alcohol effect on a 12 to 16 percent mead is large enough that the corrected refractometer figure is a rough guide only.

Mead fermentations are warm and slow, and a reading pulled from an active must at 26°C is 0.002 low on a 20°C hydrometer. Enter the sample temperature for both readings. The most useful number this calculator gives a mead maker is not the ABV, it is the gravity gap that tells you whether the yeast is near its alcohol tolerance, which is where the sweetness of the finished mead is decided.

The full Terrill correction and the hydrometer temperature polynomial, with their references, are on the general fermentation ABV calculator. For the reasoning behind temperature correction see hydrometer temperature correction.

Worked example. A traditional mead starts at 1.110 and finishes at 1.004. Balling gives 76.08 × 0.106 ÷ 0.665 = 12.13 percent by weight, and 12.13 × 1.004 ÷ 0.794 = 15.3 percent ABV. The simple (OG − FG) × 131.25 shortcut returns 13.9 percent, almost a percent and a half low, which is why mead makers who use it routinely under-report strength. Apparent attenuation is 0.106 ÷ 0.110 = 96 percent: the yeast was close to tolerance and stopped just short of dry, leaving a little perceptible sweetness.

Honey is close to pure sugar. Unlike grape must or wort, it supplies almost none of the assimilable nitrogen yeast need to build healthy cell walls and finish a fermentation. This single fact drives most of what makes mead behave differently from every other ferment on this site.

Without added nutrient, a mead fermentation commonly stalls partway or drags on for months while stressed yeast throw off fusel character. Staggered nutrient additions across the first third of fermentation are the standard fix rather than a single dose at the start.

Typical range: original gravity 1.090 to 1.130, often higher for a sack mead. Final gravity for a dry mead sits below 1.000, frequently 0.995 to 1.000, because honey leaves no unfermentable dextrin behind.

At these starting gravities the simple (OG − FG) × 131.25 approximation is at its least reliable. Hall notes specifically that the full Balling-derived calculation is worth using for a mead, where the two methods diverge most.

Apparent attenuation for mead is the number to watch during the ferment rather than after it. Honey is fully fermentable, so a healthy yeast under its tolerance limit takes a mead to 0.996 or lower and past 100 percent attenuation, the same as wine. Meads that finish sweet do so because the yeast reached its alcohol limit with sugar still in solution, not because the sugar was unfermentable.

That makes the starting gravity the real control. A 1.100 must with a 14 percent tolerance yeast ferments dry. The same yeast in a 1.130 must stops around 1.020 and stays sweet. Mead attenuation stalling early, before the yeast is anywhere near tolerance, almost always traces to nitrogen: honey has almost none, which is why the TOSNA nutrient schedule exists. A ferment that drops less than 0.010 in the first three days with a staggered nutrient plan in place is worth investigating for pitch rate or temperature.