Free tool
Spirit Dilution Calculator
Diluting with water lowers proof while preserving proof gallons. Enter your current volume and proof and how much water to add to see the final proof, or solve for the water needed to hit a target proof.
The formula
proof gallons = volume x proof / 100; final proof = proof gallons x 100 / final volume
Proof-gallon conservation (27 CFR 30.36). This tool uses the same calculation as the Spirit Sight platform. It is general information, not tax or legal advice.
How do you calculate dilution to a target proof?
Proof gallons stay constant when you add water. Final volume = proof gallons x 100 / target proof; water to add = final volume minus current volume.
Does adding water change proof gallons?
No. Water adds volume but no alcohol, so proof gallons are conserved while proof drops.
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