ABV Calculator for Homebrewing

By Dan Smullen

Alcohol by volume, or ABV, is the single number that tells you how strong your beer turned out. Enter your original and final gravity below and this tool works out the strength for you, using both the standard formula and the accurate high-gravity version.

Calculate your ABV

How to read your ABV result

The main figure is your alcohol by volume as a percentage. Alongside it you get apparent attenuation, which is the share of the original sugar the yeast fermented, and a calorie estimate for a 12 oz serving. Attenuation is a good sanity check: most clean beers finish somewhere between 70 and 80 percent apparent attenuation, so a reading well outside that range usually means a gravity reading is off or fermentation stalled.

A few common mistakes throw the number off more than people expect. Reading gravity at the wrong temperature is the big one, because a hydrometer is only accurate at its calibration temperature, so let the sample settle to around 68 degF or correct for temperature first. Not waiting for fermentation to truly finish is the other one: if you take a final gravity while the yeast is still working, your ABV will read low. Take two readings a couple of days apart and only trust it once the number stops moving.

What ABV is and when you need it

ABV is worked out from two gravity readings: the original gravity you take before pitching yeast, and the final gravity you take once fermentation has finished. The bigger the gap between those two readings, the more sugar the yeast turned into alcohol, and the stronger the beer.

You need this at two points in a brew. Before you brew, an ABV estimate from your target gravities tells you whether the recipe is going to land as a sessionable 4 percent pale or an 8 percent strong ale. After fermentation, your actual OG and FG give you the real figure to put on the bottle.

Standard formula vs the high-gravity (Hall) toggle

The standard formula is ABV = (OG – FG) x 131.25. It is quick, it is what most homebrew guides quote, and it is plenty accurate for everyday beers up to around 1.070 original gravity. Above that, the simple multiplier starts to undercount the alcohol, because the relationship between sugar and alcohol is not perfectly linear at high strengths.

That is what the high-gravity toggle is for. Switch it to the accurate setting and the calculator uses the Hall formula, ABV = (76.08 x (OG – FG) / (1.775 – OG)) x (FG / 0.794), which corrects for that curve. For a big imperial stout or a barleywine, the two formulas can differ by half a percent or more, so it is worth using the accurate setting on strong beers.

Gravity to ABV: the same calculation

If you have searched for a “gravity to ABV” calculator, this is it. Converting gravity to ABV means exactly what this tool does: take your original and final gravity and work out the alcohol. There is no separate formula and no separate tool needed. Enter your two gravity readings above and you have your answer.

Frequently asked questions

What is the formula for ABV?

The standard homebrew formula is ABV = (OG - FG) x 131.25, where OG is original gravity and FG is final gravity. For strong beers above roughly 1.070 OG, the Hall formula gives a more accurate figure: ABV = (76.08 x (OG - FG) / (1.775 - OG)) x (FG / 0.794).

When should I use the high-gravity toggle?

Use the standard formula for everyday beers. Switch to the Hall (high-gravity) formula for big beers, roughly OG 1.070 and above, where the simple formula starts to undercount alcohol. Both are built into this calculator.

Why does the calculator also show calories and attenuation?

Apparent attenuation tells you how much of the sugar the yeast fermented, and the calorie estimate uses a standard BJCP-style calculation from alcohol and residual extract. Both fall straight out of your OG and FG, so they are shown alongside ABV.

More homebrewing calculators

The ABV calculator is one tool in the full homebrewing suite. Whatever stage of the brew you are at, there is a calculator for it.

ABV CalculatorTurn your original and final gravity into alcohol by volume, with a high-gravity toggle.IBU CalculatorEstimate bitterness from hop weight, alpha acid, boil time and batch size using the Tinseth method.Priming Sugar CalculatorWork out the exact priming sugar for bottle conditioning from batch size, target CO2 and beer temperature.Strike Water CalculatorFind the strike water temperature to hit your mash target, plus an optional mash, sparge and total water plan.Carbonation CalculatorFind the regulator pressure to force carbonate your beer to a target CO2 level at a given temperature.Keg Carbonation CalculatorSet the right keg pressure for your beer style and serving temperature so it pours perfectly carbonated.Mash Efficiency CalculatorMeasure your brewhouse efficiency by comparing the gravity you hit against the maximum your grain bill could give.Yeast Pitch Rate CalculatorWork out how many yeast cells your batch needs from its gravity, volume and whether it is an ale or a lager.Hydrometer Temperature Correction CalculatorCorrect a hydrometer reading taken at the wrong temperature back to an accurate specific gravity.Original Gravity CalculatorCorrect your original gravity reading for temperature so your OG and later ABV are accurate.Final Gravity CalculatorCorrect your final gravity reading for temperature to know when fermentation is truly finished.Beer Recipe CalculatorScale every ingredient in a recipe up or down to a new batch size, keeping the balance intact.Batch Size CalculatorResize a recipe to your kettle or fermenter by finding the scale factor between two batch sizes.Beer Calories CalculatorEstimate the calories, alcohol and carbs in a serving of beer from its original and final gravity.Beer Line Length CalculatorWork out how much beer line you need for a balanced kegerator or draft system, based on your regulator pressure, rise and tubing size.

All homebrewing calculators

Not sure where your OG and FG numbers come from? Start with How to Read a Hydrometer and Correct Your Gravity, then see the full homebrewing calculator suite guide for how this fits with the rest of your brew day math.