The alcohol content of a distillate is typically measured with a hydrometer that measures degrees of proof. The hydrometer is accurate only at one reference temperature, typically 60ºF in the US or 20ºC elsewhere. To use such a hydrometer at arbitrary temperatures, one must correct for (i) the effect of temperature on the fluid, and (ii) the effect of temperature on the instrument. Tables for this purpose were prepared by the National Bureau of Standards and are part of American tax code (the TTB gauging manual). In the EU and associated countries similar regulations exist based on the Organization Internationale de Métrologie Légal in their Recommendation 22. The True Proof app can perform calculations based on either the TTB or the OIML standards.
In addition to proofing, the app performs gauging calculations - the determination of the amount of alcohol used for tax purposes. This is typically measured in proof gallons (US) or in liters of absolute alcohol (elsewhere). Gauging calculations can be based on weight or volume.
Dilution calculations are also supported. Calculate the amount of water needed (by weight or volume) to reduce the proof to your desired target.
Please notify us of any issues, bugs, or feature requests.