Algorithm To Calculate Alcohol Content

(O.G. * F.G.) * 100 * CF = Approximate ABV where O.G. = Original Gravity F.G. = Final Gravity CF = Conversion Factor

I use CF = 1.3. You can find the exact number somewhere Given the precision and the readability of hydrometers, this is similar to using a micrometer with a broomstick on the end of it.

Dick

Don't you mean (O.G. - F.G.) * 100 * CF = Approximate ABV

(Subtract FG from OG, not multiply them)

OG-FG*(factor)

The factor can be between 0.125 and 0.135 depending on the strength of the beer. Using 0.130 is good enough for homebrewing purposes but the following table has them all. OG and FG are used as whole numbers (eg 1040 rather than 1.040). The factor varies because in weaker beers a greater percentage of the available sugars are used for yeast growth and less is left for alcohol production.

(OG - FG) % ABV Factor Up to 6.9 Up to 0.8 0.125

7.0 - 10.4 0.8 - 1.3 0.126 10.5 - 17.2 1.3 - 2.1 0.127 17.3 - 26.1 2.2 - 3.3 0.128 26.2 - 36.0 3.3 - 4.6 0.129 36.1 - 46.5 4.6 - 6.0 0.130 46.6 - 57.1 6.0 - 7.5 0.131 57.2 - 67.9 7.5 - 9.0 0.132 68.0 - 78.8 9.0 - 10.5 0.133 78.9 - 89.7 10.5- 12.0 0.134 89.8 - 100.7 12.0- 13.6 0.135

Hmmm, yet more interesting information. How do I determine the strengh of the beer? Let's say I want to be extremely accurate in calculating the alcohol content, how do I do that? How do the commercial breweries calculate their alcohol content? Thanks.

Standardization of ingredients/processes Specific Gravity to get in the ball park Chromatography for the final quality assurance

They also employ tasters, but that doesn't address (except in the more extreme cases) the alcohol content.

Hoping to add something constructive, "Fred" typed

To accurately determine the alcohol content the alcohol from a measure of beer is evaporated and replaced with distilled water. The amount of replacement water is equal to the percentage of alcohol by volume when devided by the original volume.

Rob