---
title: "What Is Beer Attenuation? The Percentage That Decides Whether Your Beer Will Be Dry or Sweet"
description: "A Saison and a Sweet Stout start from similar original gravities but end up at opposite extremes, one very dry and the other sweet. The difference lies in how much work the yeast did and in what it left unfermented."
url: https://www.thebeertimes.com/en/what-is-beer-attenuation/
date: 2026-10-09
modified: 2026-10-09
author: "Carlos Uhart M."
image: https://www.thebeertimes.com/wp-content/uploads/2026/10/atenuacion-cerveza-densimetro.jpg
categories: ["Technology"]
tags: ["BJCP", "Brewing Beer", "Fermentation", "Technology", "Yeast"]
type: post
lang: en
---

# What Is Beer Attenuation? The Percentage That Decides Whether Your Beer Will Be Dry or Sweet

Attenuation is the percentage of the extract dissolved in the wort that, according to the gravity reading, the yeast consumed during fermentation. It is calculated by comparing the gravity before and after fermentation, and the higher it is, the less extract remains in the beer and the drier it tends to be.

![Hydrometer floating in a test cylinder of amber beer to measure gravity and calculate beer attenuation](https://www.thebeertimes.com/wp-content/uploads/2026/10/atenuacion-cerveza-densimetro.jpg)*Beer attenuation*

A Saison and a Sweet Stout start from similar original gravities but end up at opposite extremes, one very dry and the other sweet. The difference lies in how much work the yeast did and in what it left unfermented.

Contenido

- [What Is Beer Attenuation?](#What_Is_Beer_Attenuation)
- [Why Is Apparent Attenuation Higher Than Real Attenuation?](#Why_Is_Apparent_Attenuation_Higher_Than_Real_Attenuation)
- [What Determines How Much a Beer Attenuates?](#What_Determines_How_Much_a_Beer_Attenuates)
- [Dry and Sweet Beers According to the BJCP](#Dry_and_Sweet_Beers_According_to_the_BJCP)
- [What Happens When the Yeast Eats Almost Everything?](#What_Happens_When_the_Yeast_Eats_Almost_Everything)
- [Does a Highly Attenuated Beer Always Taste Dry?](#Does_a_Highly_Attenuated_Beer_Always_Taste_Dry)
- [Frequently Asked Questions (FAQ)](#Frequently_Asked_Questions_FAQ)
  - [1. What is the apparent attenuation of a beer?](#1_What_is_the_apparent_attenuation_of_a_beer)
  - [2. What is the difference between apparent and real attenuation?](#2_What_is_the_difference_between_apparent_and_real_attenuation)
  - [3. How much does a regular brewing yeast attenuate?](#3_How_much_does_a_regular_brewing_yeast_attenuate)
  - [4. Why can a beer have a final gravity below 1.000?](#4_Why_can_a_beer_have_a_final_gravity_below_1000)
  - [5. Does more attenuation mean more alcohol?](#5_Does_more_attenuation_mean_more_alcohol)
- [Recommended](#Recommended)

## What Is Beer Attenuation?

Before fermentation, wort is water with sugars and other malt substances dissolved in it, which is why it is denser than water. The brewer measures this original gravity (OG) with a hydrometer or a refractometer.

The yeast consumes part of those sugars, produces ethanol and CO2, and the gravity drops. The reading at the end of fermentation is the final gravity (FG).

Apparent attenuation expresses how much the gravity dropped relative to what was dissolved at the start.

\text{AA} = \dfrac{\text{OG} – \text{FG}}{\text{OG} – 1} \times 100

With an original gravity of 1.050 and a final gravity of 1.010, the calculation gives 80%, the same example [Craft Beer & Brewing](https://www.beerandbrewing.com/everything-you-need-to-know-about-attenuation) uses in its 2017 guide.

\text{AA} = \dfrac{1.050 – 1.010}{1.050 – 1} \times 100

\text{AA} = \dfrac{0.040}{0.050} \times 100 = 80\%

This is the figure yeast manufacturers publish on their technical data sheets and the one used in brewing practice.

## Why Is Apparent Attenuation Higher Than Real Attenuation?

The hydrometer doesn’t measure only the sugar that remains. It also picks up the ethanol, which is less dense than water, 0.7893 g/cm³ at 20 °C according to [PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/702), and which lowers the reading once it is mixed into the beer.

That is why the final gravity underestimates the extract that actually remains in the beer. Apparent attenuation, in turn, overstates how much the yeast fermented.

Real attenuation corrects for this effect and is calculated in degrees Plato (°P), the unit that expresses extract as a percentage by weight. In [Brew Your Own](https://byo.com/articles/attenuation-advanced-brewing/), John Palmer gives a simple conversion between gravity and degrees Plato.

P = 260 – \dfrac{260}{\text{gravity}}

With it, the original extract (OE) and the final apparent extract (AE) in the example work out as follows.

\text{OE} = 260 – \dfrac{260}{1.050} \approx 12.38\ ^\circ\text{P}

\text{AE} = 260 – \dfrac{260}{1.010} \approx 2.57\ ^\circ\text{P}

The real extract (RE) is estimated with the Balling-derived coefficients compiled by [Brew Your Own](https://byo.com/articles/calculating-alcohol/), and from it you get the real attenuation (RA).

\text{RE} = 0.1886 \times \text{OE} + 0.8114 \times \text{AE}

\text{RE} = 0.1886 \times 12.38 + 0.8114 \times 2.57 \approx 4.42\ ^\circ\text{P}

\text{RA} = \dfrac{12.38 – 4.42}{12.38} \times 100 \approx 64\%

The beer that apparently attenuated 80% actually fermented about 64% of its extract. The ethanol that distorts the reading comes from that extract, and according to the Balling balance summarized by Gary Spedding, every 2.0665 g fermented yields 1 g of ethanol, 0.9565 g of CO2, and 0.11 g of yeast (published in [The Brewers Journal](https://www.brewersjournal.info/science-basic-beer-alcohol-extract-determinations/)).

These equations are approximations, and the coefficients vary slightly depending on the source. A 2009 study in the [Journal of the Institute of Brewing](https://doi.org/10.1002/j.2050-0416.2009.tb00387.x) reviewed them using 532 pilot-plant and commercial brews (Cutaia, Reid, and Speers).

## What Determines How Much a Beer Attenuates?

Palmer distinguishes two ways of controlling it, the fermentability of the wort, which depends on the ingredients and the mash, and the performance of the yeast.

During mashing, [the malt enzymes](https://www.thebeertimes.com/en/what-are-brewing-enzymes-and-what-role-do-they-play-during-mashing/) break down the starch. Beta-amylase releases maltose, which the yeast ferments, and alpha-amylase splits the starch into longer chains, the dextrins, which a regular brewing yeast cannot use.

Temperature decides which of the two does more of the work. In a study of commercial malts published in 2005 in the [Journal of the American Society of Brewing Chemists](https://doi.org/10.1094/ASBCJ-63-0185), wort fermentability peaked with a 65 °C mash in every malt analyzed (Evans et al.).

Palmer explains that beta-amylase denatures above 66 °C. A [higher-temperature mash](https://www.thebeertimes.com/en/single-infusion-vs-step-mashing-what-is-their-impact-on-the-final-beer/) leaves more dextrins and less fermentable sugar, and the beer finishes at a higher final gravity.

The yeast sets the other limit. Each strain ferments a different share of the wort sugars, and manufacturers publish its apparent attenuation on their technical data sheets.

| Yeast | Manufacturer | Type | Stated attenuation |
| --- | --- | --- | --- |
| WLP001 California Ale | White Labs | American ale | 73 to 85% |
| [SafAle S-04](https://fermentis.com/en/product/safale-s%e2%80%9104/) | Fermentis | English ale | 74 to 82% |
| Wyeast 3711 French Saison | Wyeast | Saison, var. diastaticus with STA1 | 77 to 83% |
| SafAle US-05 | Fermentis | American ale | 78 to 82% |
| LalBrew Nottingham | Lallemand | English ale | 78 to 83% |
| [SafLager W-34/70](https://fermentis.com/en/product/saflager-w-34-70/) | Fermentis | Lager | 80 to 84% |
| [SafAle BE-134](https://fermentis.com/en/product/safale-be-134/) | Fermentis | Saison, var. diastaticus | 89 to 93% |

Data from the technical data sheets and product pages of [White Labs](https://www.whitelabs.com/yeast-single?id=101&type=YEAST), [Fermentis](https://fermentis.com/en/product/safale-us-05/), [Wyeast](https://wyeastlab.com/product/french-saison/), and [Lallemand](https://shop-us.lallemandbrewing.com/lalbrew-nottingham-yeast-11g-sachet-box-of-50-10108--77--11), accessed on October 9, 2026.

The ranges are measured under each manufacturer’s test conditions. Fermentis, for example, states the US-05 figures for a standard wort at 20 °C, and in a real recipe the number changes with the mash, the fermentation temperature, and the amount of yeast pitched.

## Dry and Sweet Beers According to the BJCP

The 2021 BJCP style guidelines list the original and final gravity of each style. Attenuation is not included, and the table below calculates it from the midpoint of each range.

| Style (BJCP 2021) | Original gravity | Final gravity | Apparent attenuation at the midpoint |
| --- | --- | --- | --- |
| [American Light Lager](https://www.bjcp.org/style/2021/1/1A/american-light-lager/) | 1.028 to 1.040 | 0.998 to 1.008 | 91.2% |
| [Saison](https://www.bjcp.org/style/2021/25/25B/saison/) | 1.048 to 1.065 | 1.002 to 1.008 | 91.2% |
| [American IPA](https://www.bjcp.org/style/2021/21/21A/american-ipa/) | 1.056 to 1.070 | 1.008 to 1.014 | 82.5% |
| [Brut IPA](https://www.bjcp.org/style/2021/21/21B/specialty-ipa-brut-ipa/) | 1.046 to 1.057 | 0.990 to 1.004 | 105.8% |
| [Doppelbock](https://www.bjcp.org/style/2021/9/9A/doppelbock/) | 1.072 to 1.112 | 1.016 to 1.024 | 78.3% |
| [Sweet Stout](https://www.bjcp.org/style/2021/16/16A/sweet-stout/) | 1.044 to 1.060 | 1.012 to 1.024 | 65.4% |

Gravities from the BJCP 2021 guidelines, with a link to each style’s entry. The last column is a The Beer Times calculation and describes the style, not a specific beer.

American Light Lager and Saison sit at the top, above 90%, which is why they tend to be perceived as dry. At the other extreme is Sweet Stout, which, according to the BJCP, is often brewed with added lactose for residual sweetness.

Brut IPA goes past 100% because its final gravity can drop below 1.000. The yeast did not consume more extract than was there, and what actually happens is that ethanol, being lighter than water, pulls the reading below that of pure water.

## What Happens When the Yeast Eats Almost Everything?

Saccharomyces cerevisiae var. diastaticus carries the STA1 gene, which encodes a glucoamylase that the yeast secretes outside the cell. With it, the yeast breaks down dextrins and starch that a regular brewing yeast leaves in the beer, according to a 2020 review in [Applied Microbiology and Biotechnology](https://pmc.ncbi.nlm.nih.gov/articles/PMC7162825/) (Krogerus and Gibson).

As a contaminant, it can keep fermenting in the bottle or can. The authors note that this raises the CO2 and alcohol, dries out the beer, and in extreme cases causes gushing and exploding packages.

Having the gene is not enough to predict the problem. A 2018 study of 19 isolates, published in [FEMS Yeast Research](https://doi.org/10.1093/femsyr/foy023), found no relationship between the presence of STA1 and each strain’s spoilage potential (Meier-Dörnberg et al.).

Its attenuation is not always extreme either. The Wyeast 3711 in the table, which its manufacturer identifies as diastaticus with the STA1 gene, lists an attenuation of 77 to 83%.

Some diastaticus strains are sold specifically for brewing very dry [Saison beers](https://www.thebeertimes.com/en/saison-history-and-origins-of-the-beer-of-ancient-belgian-farmers/), such as the BE-134 in the table.

Brut IPA reached the same dryness by another route. In late 2017, Kim Sturdavant, brewmaster at Social Kitchen & Brewery in San Francisco, brewed an IPA with amyloglucosidase, an enzyme that converts dextrins into fermentable sugar, and ended up with a beer at 0 °P, according to [Craft Beer & Brewing](https://www.beerandbrewing.com/the-birth-of-the-brut-ipa), which in 2018 credited him with creating the style.

The 2021 BJCP guidelines include it among the [Specialty IPA](https://www.bjcp.org/style/2021/21/21B/specialty-ipa-brut-ipa/) styles and mention enzymes such as amyloglucosidase among its ingredients.

## Does a Highly Attenuated Beer Always Taste Dry?

Not always. Attenuation tells you how much extract remains, and the perception of sweetness also depends on bitterness, alcohol, and carbon dioxide.

Researchers at the University of Nottingham tested a model beer with a trained panel and found that CO2 suppressed sweetness and ethanol enhanced it (Clark et al., 2011, [Chemosensory Perception](https://doi.org/10.1007/s12078-011-9087-3)).

The BJCP guidelines also point to the hops. For [Doppelbock](https://www.bjcp.org/style/2021/9/9A/doppelbock/), a dense and malty beer, the guidelines make clear where the sweetness comes from.

> The impression of sweetness comes from low hopping, not from incomplete fermentation.

With [Saison](https://www.bjcp.org/style/2021/25/25B/saison/), the opposite happens. The guidelines warn that its high attenuation can make the beer seem more bitter than its IBUs would suggest.

What remains unfermented is not all sweet sugar either. Dextrins added up to between 15 and 30 g/L in the five commercial pilsners analyzed in a 2024 study in the [Journal of the Institute of Brewing](https://doi.org/10.58430/jib.v130i3.56) (Michiels et al.), and another paper from 2025 links them to palate fullness (Moreno Ravelo et al., [Current Research in Food Science](https://doi.org/10.1016/j.crfs.2025.101118)).

A less attenuated beer tends to have more body, and [mouthfeel](https://www.thebeertimes.com/en/what-is-beer-mouthfeel-definition-fundamentals-and-associated-terms/) is a perception distinct from sweetness. That is why attenuation is a good starting point for anticipating whether a beer will be dry or sweet, and tasting, which brings together [taste and flavor](https://www.thebeertimes.com/en/difference-between-taste-and-flavor-beer/), settles the question.

## Frequently Asked Questions (FAQ)

### 1. What is the apparent attenuation of a beer?

It is the percentage of the extract dissolved in the wort that, according to the hydrometer reading, disappeared during fermentation, and it is calculated by subtracting the final gravity from the original gravity and dividing by the original gravity minus 1. A beer that goes from 1.050 to 1.010 has 80% apparent attenuation.

### 2. What is the difference between apparent and real attenuation?

Apparent attenuation uses the direct hydrometer reading, which ethanol lowers because it is less dense than water, and real attenuation corrects for that effect with the real extract, so it is always lower. In the example going from 1.050 to 1.010, apparent attenuation is 80% and real attenuation is around 64%.

### 3. How much does a regular brewing yeast attenuate?

The non-diastaticus ale and lager yeasts in the table list between 73 and 85% apparent attenuation on their technical data sheets. Some diastaticus strains, which also ferment dextrins, go further, such as Fermentis BE-134, at 89 to 93%.

### 4. Why can a beer have a final gravity below 1.000?

Because ethanol is less dense than water. When the yeast ferments almost all the extract, as in a Brut IPA, the alcohol pulls the reading below 1.000 and apparent attenuation goes past 100%.

### 5. Does more attenuation mean more alcohol?

At the same original gravity, yes. Higher attenuation means the yeast turned more extract into ethanol and CO2, which is why highly attenuated beers usually have a higher ABV than others with the same starting gravity.

## Recommended

- [Does Beer Have Sugar? Why Traditional Brews Have Almost None and Non-Alcoholic Ones Do](https://www.thebeertimes.com/en/does-beer-have-sugar/)
- [What Is Drinkability in Beer and How to Recognize It](https://www.thebeertimes.com/en/what-is-drinkability-in-beer/)