Work out the ABV of your wash from a hydrometer reading. Enter original gravity (OG) and final gravity (FG) and Broover's free ABV calculator returns the alcohol by volume using the Hall formula — the one that stays accurate across the strong-wash range distillers actually ferment.
The formula most calculators use — (OG − FG) × 131.25 — is a linear approximation calibrated for beer-strength worts. It holds up to roughly 7% ABV, then it systematically under-reads: the stronger the wash, the more alcohol it misses. Distilling washes routinely finish at 8–15% and sugar washes push higher still, which is exactly where the linear estimate goes wrong.
Broover uses the Hall formula, a higher-order fit that tracks the real OG-to-ABV relationship across the 5–25% range. For a wash that finishes near 12% ABV you can be a full percentage point off with the linear formula — and that error propagates straight into your pure-alcohol yield and dilution maths downstream.
Take a hydrometer reading before you pitch (OG) and another once fermentation finishes (FG). Enter both and the calculator returns the ABV. There is also a wash-side estimate that predicts final ABV from a measured OG at a typical finish gravity of 0.995, so you can plan before the ferment is done. Metric or US units, no signup, runs in your browser.
Once you know the wash ABV, the rest of the maths follows: pure-alcohol litres (volume × ABV) for yield and excise, strip/spirit-run recovery to plan your cuts, and contraction-correct dilution to take the distillate down to bottling strength. They are all in Broover's free calculator set, and the full app threads them into a wash-to-bottle workflow with provenance.
Open the free distilling calculators to convert OG/FG to ABV now — no signup. Or see how Broover works for the full distilling workflow.