ABV from Gravity Calculator

About this calculator

Homebrewers measure the sugar content of their wort before and after fermentation with a hydrometer, recording the original gravity (OG) — the density before yeast is pitched — and the final gravity (FG) after fermentation finishes. Because yeast converts sugar into alcohol and carbon dioxide, the drop in gravity is a direct proxy for how much sugar was fermented, and a simple formula, ABV ≈ (OG − FG) × 131.25, converts that drop into an approximate alcohol-by-volume percentage.

This calculation is a staple of home beer and wine making because commercial alcohol meters are expensive and destructive, while a hydrometer reading takes seconds and costs almost nothing. Brewers use it to confirm fermentation has actually finished (gravity should stabilize over consecutive days), to hit a target ABV for a recipe, and to compare batches made with different malts, sugars or yeast strains. The formula is an approximation rather than an exact chemical measurement — more precise methods account for the nonlinear relationship between gravity and alcohol at higher ABVs — but it is accurate enough for virtually all homebrew purposes.

This calculator takes your original and final gravity readings and returns the estimated ABV of your batch.