When you’re crafting a sweet alcoholic drink— such as a liqueur, cocktail, or cream — it’s tempting to calculate its alcohol percentage simply from the volumes of the ingredients and their respective alcohol strengths.
However, adding sugar complicates things: once dissolved, sugar takes up part of the mixture’s total volume, which skews the calculations.
Once the ingredients are mixed, an uncertainty remains:

❓ Will the final alcohol content be the one I had predicted?

In other words

❓ Can we predict the final ABV (alcohol by volume) of a sweet alcoholic preparation using only its initial composition data (water, alcohol, sugar)?

And more to the point:

❓ Why does the presence of sugar make calculating the alcohol content more complicated?

To answer these questions, it is necessary to understand the mechanisms by which sugar dissolves in a water–ethanol mixture and how to simulate its effects.

Sugar Solubility: What’s Really Going On?

When sugar dissolves, it takes up its own space — changing the total volume of your drink.
That’s why calculations based only on alcohol and water volumes can easily be thrown off.

In most recipes, the sugar in question is saccharose (sucrose) — either as a syrup (from cane or beet) or in crystalline form.
Scientists have studied how sucrose dissolves in pure water at 20 °C and have even measured its specific volume — the space taken up by a given weight of dissolved sugar.

But what happens when ethanol is in the mix?

For distillers, bartenders, and cocktail lovers, the answer matters: it’s the key to fine-tuning a recipe without oversweetening or misjudging the final ABV.
Unfortunately, there’s still a gap — the available research doesn’t give us enough hard data to predict exactly what’s going on.

Filling the Data Gap with Hands-On Experiments

To make up for the shortage of practical data, we teamed up with Labox Applications to run a series of experiments.

Our goals were clear:

– Measure how much space sucrose actually takes up in a water–alcohol mix, depending on:

• Its concentration and the ethanol percentage
• The presence of other compounds in the alcohol — tannins, esters, aromas

– Get a deeper understanding of how dissolution works

– Test whether we can reliably calculate the final ABV just from the starting amounts of sugar, water, and alcohol

In the second part of this article, you’ll find the full story — the literature review, the experiments, and our conclusions — all laid out in detail.

Conclusions and Practical Application of these Experiments

By providing a better understanding of the mechanisms of sucrose dissolution in water–ethanol solutions, this work has enabled us to determine the volume occupied by dissolved sucrose and thus to take it into account when calculating the final alcohol content.
It also made possible the development of a simple-to-use application designed to create or adjust recipes for sweet alcoholic beverages: Boxette «Creation of Liqueurs, Cocktails ».

To discover here: Demo Boxette Liqueurs-Cocktails

This Boxette precisely calculates the quantities of the different ingredients — including alcohols, water, and sugar (including crystalline sugar) — needed to obtain:
• the correct volume,
• the correct alcohol content,
• the correct sugar content,
… while taking into account the available ingredients and certain constraints related to them.

🔴 It is based on an intelligent algorithm, OPTIMIX, capable of optimizing your recipes using your stock (in volume or in % pure alcohol).

🔴 It is a practical alternative to sometimes costly methods for analyzing alcohol content.

Presentation of the Literature Review and Experiments Conducted with Labox Applications

1. Mechanism of sucrose dissolution in water

It may seem like a simple topic, but research is still ongoing to fully understand this phenomenon.
Here is a summary of what we know about the mechanism of sucrose dissolution in water, in an effort to better understand how it dissolves in a water–alcohol mixture.

1 Sucrose is a polar molecule with 8 hydroxyl (-OH) groups.

Figure 1: Formula of sucrose and 3D representation

Black spheres = Carbon (C) — Red spheres = Oxygen (O) — White spheres = Hydrogen (H)

2 The hydroxyl (-OH) groups form bonds between sucrose molecules, ensuring the cohesion of the crystal.

Figure2: Linking of two sucrose molecules to build a crystal

3 This structure is held together by interactions between hydrogen atoms and oxygen atoms, known as “hydrogen bonds.”

These bonds can be:

• Intramolecular, within the same sucrose molecule (see the dotted lines in Figure 3)
• Intermolecular, linking two separate sucrose molecules together (see the dotted lines in Figure 4)

4 Water — being highly polar — can break these bonds and dissolve sugar.

When sucrose is introduced into water, the water molecules can interact with the 8 –OH groups and the 3 oxygen atoms of the glycosidic bonds (C–O–C) in the sugar, gradually breaking down the crystalline network of the solid sugar.
The dispersion of sucrose molecules in water corresponds to dissolution.

Figure 5: Interaction of water with sucrose

Consequence :

In theory, in a simplified water/sucrose model, 11 water molecules can interact with a sucrose molecule to enable its dissolution, replacing sugar–sugar interactions (in the crystal) with water–sugar interactions (1).

In practice, it is observed that for a given volume of water, when sucrose is gradually added, the number of water molecules able to bind to sucrose decreases significantly, due to sugar–sugar interactions becoming progressively harder to break (2).

As a result, studies have shown that the ratio of water molecules bound to sucrose decreases as sucrose concentration increases, and does not exceed 6 at 20 °C (3).

❓Once it’s dissolved, how much space does sucrose actually take up?

2. Volume occupied by dissolved sucrose in water

The volume occupied by a given mass of dissolved solid is called the “apparent specific volume.” It depends on many factors. For sucrose in water at 20 °C, studies put the “apparent massic volume” between 0.61 and 0.63 cm³ per gram (2) (4).

It is possible to calculate its value in the syrups used by professionals in the spirits industry, based on the data provided in the technical sheets of these syrups.

Example 1 : Calculation of the apparent specific volume of sucrose in PECNER syrup

1 Water mass from the technical sheet

• Syrup density: 1320 g/L
• Sucrose content: 860 g/L
• Since 1 L of syrup weighs 1320 g, the water mass is:
  1320 – 860 = 460 g of water.

2  Water volume

• Water density: 998 g/L
• Water volume = 460 / 998 = 461 L.

3 Sucrose volume in the syrup

• 1 L total – 0.461 L water = 0.539 L of sucrose

4 Apparent specific volume
0.539 L / 860 g = 0.000627 L/g, or 0.627 cm³/g.

Example 2 : Calculation of the Apparent Specific Volume in MENEAU Syrup 

From the Meneau syrup technical sheet:

• Density: 1375.1 g/L
• Sucrose content: 890 g/L

Running the same calculation as in Example 1 gives an apparent specific volume of 0.631 cm³/g.

Both examples confirm what the literature suggests: in water at 20 °C, sucrose’s apparent specific volume sits in the 0.61–0.63 cm³/g range (2) (4).

❓What about the volume occupied by sucrose in recipes based on water and ethanol?

❓ What information does the scientific literature provide?

3. Volume occupied by dissolved sucrose in a water/ethanol mixture

3.1. Literature Data

Due to the lack of experimental data, a relatively recent 2018 study (5) was conducted by researchers in the pharmaceutical industry. This study focuses on the apparent specific volume of sucrose in solution at 25 °C, in various water–co-solvent mixtures, including ethanol.

The authors concluded that a mean value of 0.632 cm³/g ± 0.008 can be used as a practical estimate for the apparent specific volume of sucrose in the mixtures studied, and more specifically 0.625 cm³/g ± 0.008 in water–ethanol mixtures at 25°C.

❓ What about at 20 °C?

3.2. Practical Studies for Calculating the Apparent Specific Volume of Sucrose at 20 °C in a Water/Ethanol Mixture

In the absence of scientific data at 20 °C — the international legal metrology reference temperature — we carried out, with the Labox Applications team, a series of 20 tests at 20 °C (±1 °C), covering water/ethanol mixtures from 0 to 90 % ABV.

The data from Pecner and Meneau syrups were taken into account in these calculations.

Some experiments, carried out at alcohol and sugar concentrations far beyond common usage, aimed to explore the limits of sucrose solubility in a water/ethanol mixture.

For some solutions, we measured the final ABV to double-check the accuracy of our calculations.

Summary of the Test Protocol

1 Prepare the water-alcohol base

• Start with neutral alcohol at 96.4% ABV
• Dilute to target strengths at 20 °C ± 1 °C
• Measure each solution’s ABV (ABVss) and density (VMss) after contraction, using a portable digital densimeter

2  Add cristalline sugar

• Weigh into a 100 ml volumetric flask
• Adjust mass to hit target concentrations

3  Add the water-alcohol solution

• Fill to the calibration line
• Record the mass added

🧮 Calculations

• Volume of water–alcohol solution added = mass / density (VMss)
• Volume occupied by sugar = Total volume (100 ml) – Actual volume of water–alcohol added
• Apparent specific volume of sugar = sugar mass / volume occupied by sugar
• Final ABV (% vol.) = Volume of water–alcohol solution × ABVss / 100

Test Results

Figure 6 shows the alcohol content/sugar concentration pairs that were tested.
The blue dots mark the cases where the sucrose didn’t fully dissolve.

As expected, the more ethanol in the mix, the less sucrose it can dissolve. Above 15% ABV, the drop in solubility looks pretty linear.

The calculation of the apparent specific volume for each test (in cases of complete or near-complete solubility) consistently yielded values between 0.618 and 0.630 cm³/g, with an average of 0.624 cm³/g ± 0.006 at 20 °C in water–ethanol mixtures.

These numbers line up perfectly with:

• values measured in pure water at 20 °C (0.61–0.63 cm³/g) (2) (4)
• and the 2018 published results for water–ethanol at 25 °C (0.625 cm³/g ± 0.008) (5).

No significant trend in apparent specific volume variation was observed as a function of either alcohol content or sucrose concentration (Figures 7 and 8).

Interpretation of the results for the apparent specific volume of sucrose in water–ethanol mixtures

The results suggest that the volume occupied by sucrose in water–ethanol mixtures remains essentially constant, regardless of the ethanol percentage.

By using the number of water molecules (Rm) needed to dissolve one sucrose molecule in water — theoretically 11, but in practice a maximum of 6 — it is possible to calculate the solubility limit of sucrose in a water–ethanol mixture under these two assumptions.

This yields the following representation (Figure 9).

The resulting graph shows that, in tests close to saturation, sucrose requires more water than the theoretical threshold to dissolve.

This is probably due to water’s strong affinity for ethanol. The portion of water bound to ethanol is therefore unavailable for dissolving sugar.

In short, only the free water is available to hydrate sucrose.

Consequence:
In sweet alcoholic drinks, part of your water is “locked up” with ethanol — so the sugar can only dissolve using what’s left free (Figures 11).

This study also shows that, 90% ABV and above, there are not enough water molecules available to fully hydrate sucrose. We calculated that the number of free water molecules is then only about 30% of the amount needed to dissolve sucrose.
On top of that, the sucrose’s three-dimensional hydrogen-bond network becomes so disrupted that it can no longer bond effectively.

Note: For most real-world recipes — creams, cocktails, liqueurs — the alcohol levels fall well within the safe zone shown in Figure 9, so this solubility limit isn’t an issue.

❓What about the influence of other compounds present in spirits on the solubility of sucrose and its apparent specific volume?

4. Effect of volatile compounds in spirits on the apparent specific volume of sucrose

As far as we know, no published research looks at whether the natural compounds in spirits can change sucrose’s apparent specific volume.

When making liqueurs, cocktails, or other sweet alcoholic drinks, the base spirits are usually chosen for clean analytical profiles — little to no wood aging, low tannin levels, aromatic but light in certain volatile compounds (like fatty acids) that could cause stability issues.

To assess whether certain volatile compounds naturally present in spirits — such as higher alcohols, aldehydes, esters, or even some fatty substances — could influence sucrose solubility and its apparent specific volume, an additional experiment was conducted.

Choice of base alcohol
A rum aged 3 years in oak barrels, originally at 70% ABV, selected because its aromatic profile is similar to what’s used in many liqueur recipes.

It was reduced to 48% ABV, then sweetened to reach about 35% ABV in the final mix.
The sugar content added was 430 g/L, right at the solubility limit for that alcohol strength.

This rum had the following characteristics:

• Total aldehydes (ethanal/acetal expressed as ethanal): 7 g/hl AP
• Ethyl acetate: 66 g/hl AP
• Higher alcohols: 183 g/hl AP
• Volatile acidity: 9 g/hl AP
• Total volatile substances: 264 g/hl AP
• Tannins: 150 mg/L (kept moderate to avoid any risk of precipitation or color alteration)

This test is shown in Figure 10, at the intersection of 35% abv / 430 g/L sugar.

Test results:

• The sugar dissolved completely, event with the rum’s aromatic richness.
• The apparent specific volume came out to 0.624 cm³/g, matching perfectly with the values from our pure water–ethanol tests.

Conclusion :
For the kinds of base spirits typically used in liqueurs, cocktails, or other sweet alcoholic drinks, having volatile compounds or tannins at normal levels doesn’t make a measurable difference to:
• how well sucrose dissolves, or
• the space it takes up once dissolved.

5. Confirmation by measuring the alcohol content of the mixtures prepared for the test

To confirm that our method could accurately predict the final ABV, we distilled four of the earlier test samples — including the rum-based one.
Why distillation? In a sugar-containing water–ethanol mix, you need to measure the ABV in the distillate, where only water and ethanol remain.
We used a semi-automatic steam distillation unit (DE 2000 de chez DUJARDIN-SALLERON), for precise results with no alcohol loss.
ABV was then measured using an Anton Paar portable meter (DMA 35 de chez Anton Paar), accurate to ±0.1% ABV when properly calibrated.

For a few tests where the final ABV could have exceeded 25%, we diluted the sample by half first. (See our three other blog posts for more on ABV testing methods.)

The table below shows the results:

Observation:
For three of the tests, the predicted and measured ABV differed by just 0.1% vol. In one case, the gap was 0.3% vol..
Given that the measurement uncertainty was ±0.2% for undiluted samples (tests 19 and 20) and ±0.3% for diluted ones (tests 17 and 18), all differences were well within the expected margin of error.

This means our ABV prediction method is accurate enough for developing sweet alcoholic beverage recipes.

We also confirmed that any contraction or expansion caused by adding sugar to a water–ethanol mix is negligible for ABV prediction purposes.
Since the water bound to ethanol isn’t available to dissolve sucrose, it’s safe to assume that the density of the “ethanol-bound water” portion stays constant — or at least doesn’t change enough to affect ABV readings.

However, when mixing water and alcohol, or when adding another alcohol or water to an existing water–alcohol mixture, it is necessary to first calculate the percentage of contraction or expansion of this solution before calculating the sugar’s effect. For this calculation, us the Boxette:  “Alcohol content adjustment“.

6. General Conclusion

This study confirms that by taking 0.625 cm³/g as sucrose’s apparent specific volume, it is possible to predict the final ABV with reliable accuracy.

Sucrose dissolves almost entirely based on how much free water is available — it dissolves in water, not ethanol — and the space it takes up (about 0.625 cm³/g) stays constant no matter the ABV.

By combining this fixed volume value with the known contraction effects of water–ethanol mixes, you can precisely predict the ABV of a sweet drink recipe, whether you’re adding commercial crystalline sugar or syrup.

It also works the other way around: if you know the target ABV and sugar content for a final volume at 20 °C, you can work out exactly how much water, pure alcohol, syrup, or sucrose to add.