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Proof gallons calculator

Turn a measured volume and its proof into wine gallons and proof gallons.

The Proof Gallons calculator converts a measured volume and its proof into two figures: the wine gallons (the plain physical volume, on the U.S. gallon basis) and the proof gallons (the tax unit — one gallon of spirits at 100° proof). It's the everyday conversion behind gauging a tank, a barrel, or a fill, and it's the definition every proof-gallon figure in Brewstiller rests on: proof gallons = wine gallons × proof ÷ 100.

Like all of the Tools calculators, it's free, needs no account, and computes right in your browser.

Open the calculator

  • On the public site: in the top navigation choose Tools, then on the Proof Gallons card choose Open calculator.
  • Inside the app: in the navigation choose Tools, then on the Proof Gallons card choose Open calculator.

Convert a volume to proof gallons

  1. In the Volume field, enter the measured volume — any number of 0 or more.
  2. From the Unit list, choose the unit that volume is in: Milliliters (mL), Liters (L), U.S. gallons, Wine gallons, Barrels (31 U.S. gal), or Fluid ounces.
  3. In the Proof field, enter the proof — a number from 0 to 200 (proof is twice the ABV percentage, so 150° proof is 75% ABV).
  4. The result appears as soon as both fields hold valid numbers: Wine gallons and Proof gallons, side by side. There's no button to press — it recomputes as you type.

If you enter a volume below 0, the field shows Enter a number of 0 or more. If you enter a proof outside 0–200, it shows Enter a proof between 0 and 200. Fix the flagged field and the result returns.

Worked example

Gauging 5 U.S. gallons of a 150° proof spirit:

  1. Volume: 5
  2. Unit: U.S. gallons
  3. Proof: 150

The calculator shows Wine gallons 5 and Proof gallons 7.5 — because 5 × 150 ÷ 100 = 7.5.

When to reach for it

Reach for Proof Gallons whenever you have a physical volume and a proof and need the proof gallons — checking a gauge before you write it down, sizing a barrel entry, or sanity-checking a number on a report. If you gauge by weighing the package instead of measuring its volume, use the Weight-to-proof-gallons calculator. If your proof reading was taken at a temperature other than 60 °F, correct it first with the Temperature correction calculator, then bring the true proof here.

The calculator notes on-screen that it's a quick estimate for reference — a tool, not an official TTB filing or gauge record.