Blending, Proofing and Dilution Calculations for Ethanol-Water


If you need to include sugar in your blending or proofing calculations, please see the blending calculator in AlcoDens LQ.

The process of diluting a high strength spirit to a specific proof is usually known as "proofing the spirit". Calculating the quantity of water required is complicated by the shrinkage that occurs when alcohol and water are mixed. AlcoDens takes this into account and the effects are illustrated in the examples below.

Blending to a target strength

This example shows a blending calculation where a known quantity (3 m) of distilled spirit at 95.5% ABV is to be diluted with pure water (0% ABV) to achieve a target blend of 40% ABV. Note that the calculated quantity of water (4.37 m) plus the 3 m of spirit gives 7.16 m blend because of the shrinkage.

Blending two known quantites

This second blending example illustrates the AlcoDens capabilitity to determine the result of blending two sources of known quantity and strength. Here we have an instance where the shrinkage is actually negative and the total volume is greater than the sum of the two sources.


In AlcoDens the blending, proofing, dilution and fortification calculations are done rigorously and take into account the shrinkage (contraction) that occurs when ethanol and water are mixed. This makes it much more accurate than the Pearson Square method. Although Pearson Square may give acceptable errors when blending wines of almost the same strength, it gives significant errors when diluting or proofing distilled alcohol with water, or when fortifying wine with neutral spirit.

The AlcoDens blending and dilution calculations are as accurate as can be achieved with the TTB Gauging Tables, but AlcoDens is vastly more flexible because you can select from a wide range of units and it eliminates the error-prone interpolation required when working between data points in the TTB Tables. AlcoDens also makes it easy to work with volumes that are not measured at 60F.

Although these calculators work with only two sources at once, they both allow you to blend more than 2 sources together by dealing with them sequentially.

Like all the AlcoDens calculators, the Blending Calculators can use either the OIML (in vacuum) or the TTB (in air) model. The model currently in use is always highlighted by the button with the red text in the top right corner.

In all the blending, proofing and dilution calculations the spirit strengths can be specified as densities (SG), Mass %, Volume % (ABV) or Proof. The quantities can be specified in mass or volume terms. The units of measure for the strengths and quantities can be mixed in any combination - for example you can calculate the mass of water to be added to a known mass or volume of 130 Proof spirit to achieve a final required volume at 40 ABV.