ABV Calculator

How it works

This ABV calculator works for beer, cider, wine and mead alike — it only needs two hydrometer readings, so you don’t need separate tools for each beverage. Original gravity (OG) measures the density of your must or wort before fermentation starts, when it’s full of unfermented sugar. Final gravity (FG) measures the same liquid once fermentation has finished converting most of that sugar into alcohol and CO₂. The bigger the drop between the two readings, the more sugar was fermented, and the higher the alcohol content.

The formula this abv estimator uses is the standard, widely-used homebrew approximation:

ABV % = (Original Gravity − Final Gravity) × 131.25

So a wort that starts at 1.050 and finishes at 1.010 has dropped 0.040 gravity points, giving 0.040 × 131.25 = 5.25% ABV. This is intentionally the simple, standard version of the formula that most brewers already know as their go-to abv calc — it’s accurate for typical gravities. For very high-gravity brews, above roughly 1.070 OG, a more precise (and more complex) formula exists because the simple linear approximation drifts slightly at extreme sugar concentrations, but for the vast majority of beer, cider, wine and mead recipes the standard formula above matches what you’d measure with lab equipment closely enough to plan a batch or label a bottle.

Once ABV is known, this tool also converts it into standard drinks per serve, using Australia’s official definition of a standard drink: 10 grams of pure alcohol, based on an ethanol density of 0.789 g/mL, as set out by the Australian Government Department of Health’s standard drinks guide. The conversion is:

Standard drinks = (Serving volume mL × ABV % ÷ 100 × 0.789) ÷ 10

A 375mL can at 5.25% ABV therefore contains about 1.6 standard drinks — useful context whether you’re labelling a home-brewed batch or just working out how many cans is sensible for the night.

Worked example

Marcus, a home cider maker in Ballarat, Victoria, presses a batch of apples and takes an original gravity reading of 1.055 before pitching his yeast. Three weeks later, once fermentation has stopped bubbling, he takes a final gravity reading of 1.008. Plugging both into the formula: (1.055 − 1.008) × 131.25 = 0.047 × 131.25 = 6.2% ABV — a solid, fairly standard cider strength.

Marcus wants to know how that translates into serving sizes for a barbecue. He bottles most of the batch into 375mL stubbies but pours a bit into wine glasses for guests who prefer smaller serves. Using the standard drinks formula on each serving size shows a clear difference:

Serving	Volume	Standard drinks
Stubbie/can	375 mL	1.8
Wine glass	150 mL	0.7

Knowing both numbers up front means Marcus can tell guests roughly how many stubbies equal “a couple of standard drinks” before anyone starts pouring — handy information for anyone driving home afterwards.