Free tool
Angel's Share Calculator
Whiskey loses a few percent to evaporation each year, the angel's share. Enter your barrel's proof gallons, annual loss rate, and aging period to project the proof gallons (and value) lost over time.
The formula
remaining PG = starting PG x (1 - annual loss rate)^years; lost PG = starting - remaining
Industry evaporation ranges of ~2-6% per year (varies by climate, floor, and warehouse). This tool uses the same calculation as the Spirit Sight platform. It is general information, not tax or legal advice.
What is the angel's share?
The portion of aging spirit lost to evaporation, typically 2-6% per year depending on climate and warehouse position.
How do you calculate evaporation loss over years?
Compound the annual loss rate: remaining = starting x (1 - rate)^years. Over 6 years at 4%/yr a barrel loses about 22% of its proof gallons.
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