Calculator
Enter the current proof of your spirits and the proof you want to reach to see how much water to add (27 CFR §30.66).
Enter a current proof and a lower target proof to see the result.
This is a quick estimate for reference — a tool, not an official TTB filing or gauge record. It uses the 27 CFR §30.66 Table-6 method, which accounts for alcohol–water contraction when spirits and water are mixed — the water needed is more than simply subtracting volumes.
Reference tools, not a system of record. These free calculators are provided for convenience and general reference only. They are not a system of record and must not be used as the basis for any TTB or state compliance filing — even when a result is correct. Your official filings are governed by the applicable measurement and gauging methods and by your own production records.