True Proof Calculator

What this calculator does

The True Proof calculator corrects an observed hydrometer proof reading for temperature using TTB Table 1. When a proof hydrometer is read at a temperature other than 60°F, the observed proof must be corrected to determine the true proof of the spirit. This calculator applies the official TTB Table 1 correction factors to produce the true proof value used for gauging, tax determination, and production records.

How to use it

Enter the observed proof reading from your proof hydrometer and the temperature of the spirit sample in degrees Fahrenheit. The calculator applies the TTB Table 1 correction and returns the true proof. Use a calibrated proof hydrometer and an accurate thermometer for reliable results. The temperature range supported by Table 1 is 0°F to 100°F.

Calculation notes

TTB Table 1 provides correction factors for proof hydrometer readings taken at temperatures other than 60°F. For fractional temperatures, bilinear interpolation is used between the nearest table entries. The calculator assumes a clean, homogeneous spirit sample. Readings from spirits containing dissolved solids, sugars, or extraneous materials may not be accurately corrected by Table 1 alone. Always verify final proof values using approved gauging procedures.

Reference: TTB Table 1. ProofLogic uses this table methodology as a calculation reference. ProofLogic is not approved, endorsed, certified, or operated by the Alcohol and Tobacco Tax and Trade Bureau or any other government agency.

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