Apparent & Real Attenuation Calculator

How it works

Apparent attenuation = (OG − FG) ÷ (OG − 1) × 100. Real extract = 0.1808·OE + 0.8192·AE (°P). Real attenuation = (OE − RE) ÷ OE × 100. ABW = (OE − RE) ÷ (2.0665 − 0.010665·OE)

Attenuation is the share of the wort’s sugar the yeast consumed. The “apparent” version is what your hydrometer implies, but it flatters the yeast because the alcohol produced is lighter than water and pulls the final gravity down further than sugar removal alone would; real attenuation corrects for that with Balling’s relationship and is typically about 80% of the apparent figure. Yeast labs quote apparent attenuation ranges — 67–71% for a typical English strain, 73–77% for American ale yeast, 80% and up for saison and wine strains — and comparing your result with the range tells you whether the fermentation finished. The same numbers give ABV and, via the residual extract, the calorie content.

Worked example

OG 1.056, FG 1.012: apparent attenuation 78.6%, real attenuation about 64%, 5.8% ABV, roughly 185 kcal per 12 oz.

Frequently asked questions