Free tool
Spirit Blending Calculator
Blending two spirits combines their proof gallons. Enter each spirit's volume and proof to get the blended proof, ABV, and how much each contributes.
The formula
blended proof = (PG_a + PG_b) x 100 / (volume_a + volume_b), where PG = volume x proof / 100
Proof-gallon arithmetic (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 the proof of a blend?
Add the proof gallons of each spirit (volume x proof / 100), then divide total proof gallons x 100 by the total volume.
Why blend by proof gallons instead of proof?
Proof is a concentration; you cannot average it directly across different volumes. Proof gallons measure actual alcohol, so they add correctly.
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