27 CFR § 5.65 - Alcohol content.
(a) General. The alcohol content for distilled spirits must be stated on the label as a percentage of alcohol by volume. Products that contain a significant amount of material, such as solid fruit, that may absorb spirits after bottling must state the alcohol content at the time of bottling as follows: “Bottled at ____ percent alcohol by volume.”
(b) How the alcohol content must be expressed. The following rules apply to statements of alcohol content.
(1) A statement of alcohol content must be expressed as a percentage of alcohol by volume.
(i) In addition, the alcohol content in degrees of proof may be stated on a label as long as it appears in the same field of vision as the mandatory statement of alcohol content as a percentage of alcohol by volume. Additional statements of proof may appear on the label without being in the same field of vision as the mandatory alcohol by volume statement.
(ii) Other truthful, accurate, and specific factual representations of alcohol content, such as alcohol by weight, may be made, as long as they appear together with, and as part of, the statement of alcohol content as a percentage of alcohol by volume.
(i) The alcohol content statement must be expressed in one of the following formats:
(A) “Alcohol ____ percent by volume”;
(B) “____ percent alcohol by volume”; or
(C) “Alcohol by volume ____ percent.”
(ii) Any of the words or symbols may be enclosed in parentheses and authorized abbreviations may be used with or without a period. The alcohol content statement does not have to appear with quotation marks.
(3) The statements listed in paragraph (b)(2)(i) of this section must appear as shown, except that the following abbreviations may be used: Alcohol may be abbreviated as “alc”; percent may be represented by the percent symbol “%”; alcohol and volume may be separated by a slash “/” in lieu of the word “by”; and volume may be abbreviated as “vol”.
(4) The following are examples of alcohol content statements that comply with the requirements of this part:
(i) “40% alc/vol”;
(ii) “Alc. 40 percent by vol.”;
(iii) “Alc 40% by vol”; and
(iv) “40% Alcohol by Volume.”
(c) Tolerances. A tolerance of plus or minus 0.3 percentage points is allowed for actual alcohol content that is above or below the labeled alcohol content.