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 the dollar value, lost over time. This tool uses the same compounding math Spirit Sight uses for barrel loss.

PG
%/yr
yr
$

The formula

remaining PG = starting PG x (1 - annual loss rate)^years; lost PG = starting - remaining

A worked example

A barrel filled with 66.25 proof gallons losing 4% per year holds 66.25 x 0.96^6 = 51.9 proof gallons after six years. The angels took 14.4 proof gallons, roughly 22% of the fill, which is why measured loss rates belong in your valuation.

Doing this math barrel by barrel? The platform runs the same calculation on every record automatically, reconciled against the books. See it live.

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 to 6 percent per year depending on climate, floor, and warehouse position. It reduces both volume and, over time, value.
How do you calculate evaporation loss over years?
Compound the annual loss rate: remaining = starting x (1 - rate)^years. Over 6 years at 4 percent a year a barrel loses about 22 percent of its proof gallons.
How much is the angel's share worth in dollars?
Multiply the proof gallons lost by your value per proof gallon. Because loss compounds, the dollar cost grows with age, which is why it belongs in cost per barrel rather than as a year-end surprise.
Barrel cost amortization calculatorProof gallon calculatorBarrel and rickhouse managementThe angel's share (glossary)

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