Brix to Specific Gravity Converter

In short Brewing measures the same thing on three scales and recipes move between them without warning. Specific gravity compares the wort with water — 1.048 means it weighs 4.8% more. Plato and Brix both say what percentage of the weight is dissolved sugar, so 1.048 is about 12°. They are different tables built for different industries, and in the brewing range they differ by less than a tenth of a degree, so this page treats them as interchangeable and says so rather than implying a precision that does not exist. The rough conversion brewers do in their heads is gravity points divided by four, and at 48 points that gives 12° against a true 11.91 — close enough to plan with and not close enough to record. TWO THINGS ABOUT REFRACTOMETERS, AND THE SECOND IS THE IMPORTANT ONE. First, a refractometer is calibrated on sugar syrup, and wort is not sugar syrup: proteins and unfermentable dextrins bend light differently, so it reads a few per cent high. Dividing by about 1.04 corrects it, and the factor is specific to your instrument and your wort, so measure it once against a hydrometer and use your own. Second, and this is where people get hurt: ONCE FERMENTATION HAS STARTED A REFRACTOMETER READING IS NOT A GRAVITY AT ALL. Alcohol bends light in the opposite direction to sugar, so the reading is corrupted by an amount that depends on how much alcohol is present — which is the thing you were trying to measure. Published correction formulas exist. They are cubic curves fitted to particular data sets, they disagree with one another, and a wrong one hands you a confident final gravity that is simply not true. This page deliberately does not carry one. Use a hydrometer for the final reading. One more thing worth carrying: gravity points are additive over volume, so 48 points in 20 litres is the same extract as about 38 points in 25. Every dilution, top-up and boil-off calculation in brewing is that one identity.