ABV, from two readings.
Original minus final, times 131.25. A 1.050 mead finishing at 1.000 reads about 6.6%.
Original minus final, times 131.25. A 1.050 mead finishing at 1.000 reads about 6.6%.
ABV = (OG − FG) × 131.25
A hydrometer reads density; sugar consumed became alcohol and left the reading lower. The 131.25 converts the drop to volume percent — the brewer’s shortcut, and it is labeled as one, because real attenuation chemistry shifts it a little.
A mead starts at 1.050 and finishes at 1.000: (1.050 − 1.000) × 131.25 ≈ 6.6%. A cider from 1.055 to 1.010 reads (0.045) × 131.25 ≈ 5.9%. The ABV calculator runs the same line, and the mead guide shows where the readings belong in the batch.
The shortcut assumes the typical chemistry of beer and wine ferments; strong or unusual batches drift from it. For a label-ready number, the honest route is the lab — but for knowing where a batch stands, two readings beat every guess.