Free tool

Alcohol by Weight (ABW) Calculator

Convert alcohol by volume (ABV) to alcohol by weight (ABW) and proof. ABW is always lower than ABV because ethanol weighs less than water, so the same volume percentage is a smaller weight percentage. This tool uses the same conversion as Spirit Sight.

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The formula

ABW = ABV / 1.267 (approximate); proof = ABV x 2

A worked example

An 80 proof (40% ABV) vodka is approximately 40 / 1.267 = 31.6% alcohol by weight. ABW is always lower than ABV because ethanol is lighter than water.

Doing this math barrel by barrel? The platform runs the same calculation on every record automatically, reconciled against the books. See it live.

Standard approximation; exact ABW depends on the solution density at temperature. This tool uses the same calculation as the Spirit Sight platform. It is general information, not tax or legal advice.

What is the difference between ABV and ABW?
ABV is the percentage of alcohol by volume; ABW is by weight. Because alcohol is less dense than water, ABW is lower, roughly ABV divided by 1.267 for typical spirits.
How do you convert ABV to ABW?
Divide ABV by about 1.267. So 40 percent ABV is about 31.6 percent ABW, and 50 percent ABV (100 proof) is about 39.5 percent ABW.
How do you convert ABV to proof?
In the US, proof is exactly twice the ABV, so 40 percent ABV is 80 proof.
ABV to proof converterProof gallon calculatorTTB gauging calculatorProof gallon (glossary)

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