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Homebrew ABV calculator

From the original and final gravity of a fermentation, the alcohol by volume. Choose the standard, alternate or a high-ABV formula — the last is more accurate for strong beers and wines.

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The Homebrew ABV calculator turns Original gravity (OG), Final gravity (FG), Formula into Alcohol by volume, Apparent attenuation, instantly and for free. For instance, with Original gravity (OG) = 1.05, Final gravity (FG) = 1.01 and Formula = Standard (×131.25) it returns Alcohol by volume = 5.25% and Apparent attenuation = 80%.

How to use it

  1. Enter your values: Original gravity (OG), Final gravity (FG), Formula.
  2. Read the result instantly: Alcohol by volume, Apparent attenuation.

Frequently asked questions

How does the Homebrew ABV calculator work?

It takes Original gravity (OG), Final gravity (FG) and Formula and derives Alcohol by volume and Apparent attenuation from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

3 values: Original gravity (OG), Final gravity (FG) and Formula. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Original gravity (OG) = 1.05, Final gravity (FG) = 1.01 and Formula = Standard (×131.25), the calculator returns Alcohol by volume = 5.25% and Apparent attenuation = 80%. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Original gravity (OG) = 2.1, Final gravity (FG) = 2.02 and Formula = Alternate (×132.715) instead, Alcohol by volume goes from 5.25% to 10.62% — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Formula” option should I choose?

You can pick between « Standard (×131.25) », « Alternate (×132.715) » and « Advanced (high ABV) ». Each one changes what the calculator works out, so switch and compare — the default is « Standard (×131.25) ».

What does it give for smaller values?

Scaled down to Original gravity (OG) = 0.525, Final gravity (FG) = 0.505 and Formula = Standard (×131.25), Alcohol by volume comes out at 2.63%. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Cooking from a recipe that does not match your kitchen: scaling for a different number of people, converting cups to grams, and substituting what you do not have.

What is the most common mistake?

Converting a cup as if it were a volume of weight. A cup of flour and a cup of sugar differ by nearly a third in mass, so a single conversion factor gets one of them badly wrong.

What is the difference between the Homebrew ABV calculator and the Cocktail ABV calculator?

This one returns Alcohol by volume and Apparent attenuation; the Cocktail ABV calculator returns Final ABV and Total volume (ml). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Cocktail batch calculator is the closest one after this: Scale up a single cocktail into a large batch for a party.

Further reading

All guides →
ExplainerBaker's Percentage Explained: One Formula, Any Batch SizeFlour is 100 percent and everything else is measured against it. That one convention lets the same recipe scale from a single loaf to a bakery batch without a single new calculation — and yes, the percentages are supposed to add up to more than 100.How-toHow to Convert Any Oven Recipe for an Air FryerDrop 25 °F and cut the time by about a fifth — then adjust for what the food is and how full the basket is, because those two change the answer more than the rule does.ExplainerHow Much Wine for a Wedding: Work From Bottles, Not From a Rule of ThumbA 750 ml bottle pours five glasses, and guests average about one drink per hour. Everything else is arithmetic — here it is for 50 to 250 guests over three, four and five hours, with an honest range rather than a single number.GuideYeast Conversion Chart: Fresh, Active Dry and Instant, With the Actual FactorsMultiply fresh yeast by 0.4 for active dry and by 0.33 for instant. Those two numbers are the whole chart, they are King Arthur's professional figures, and they are approximate — here is how far, and what else changes when you swap.GuideThe Sourdough Timeline: An Hour-by-Hour Schedule That Fits a Real DayA full schedule from feeding the starter to slicing the loaf, and the one variable that moves every time on it. Five hours of bulk at 75 °F becomes about seven and a quarter at 68 °F.How-toHow to Double a Recipe (Without Ruining It)Doubling a recipe is more than multiplying by two. Learn the scale factor, which ingredients to scale carefully — spices, salt, leavening — and why bake time and pan size do not simply double.