Free tool
Spirit Blending Calculator
Blending two spirits combines their proof gallons, not their proof. Enter each spirit's volume and proof to get the blended proof, ABV, and how much each spirit contributes. This blending calculator uses the same proof-gallon math as Spirit Sight.
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. For 60 gal at 120 proof and 40 gal at 90 proof, that is 108 PG over 100 gal, or 108 proof.
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 and give the true blended proof.
Can I blend more than two spirits?
The same principle scales: sum every component's proof gallons and total volume, then divide total PG x 100 by total volume. This tool blends two at a time; chain it or use Spirit Sight for multi-component batches.
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