Blending wine to adjust wine chemistry can be a little tricky. Luckily there’s a handy tool you can use, Pearson’s Square, for determining the proper proportions needed to create the right balance in your final wine.

The science of blending wine using Pearson's SquareThis tool can be used for blending a wine of high alcohol and one of low alcohol content to produce a wine with a more reasonable alcohol level. It doesn’t end with alcohol though, Pearson’s Square can be used to:

  • blend wines of different acidity to create a more balanced wine
  • blend wines of different degrees of sweetness
  • calculate sugar additions to increase a finished wine’s alcohol content
  • blend wine and brandy when fortifying a wine

So how does this magical tool work? Let’s find out.

Calculating Blend Ratios

Pearson’s Square is actually a simple tool for calculating the ratios of two different wines that when mixed together result in a mixture that has the characteristics you desire. If we have two wines of different alcohol levels we can use the square to determine how much of each wine to mix together to come up with a blend that has an alcohol level of our choosing.

Here’s what Pearson’s Square looks like:

Pearson's SquareThe variable “A” represents the alcohol content of one of your blending wines while “B” represents the alcohol content of the other.  “C” represents your target alcohol level. Keep in mind that you can use this for more than just blending wines of different alcohol levels.

With this information you can calculate “D” which is the amount of wine “A” that you need. “E” represents the amount of wine “B” you need. When combined in these amounts you will have a wine with the desired alcohol level “C”.

This has been sort of abstract so let’s try and example.

Using the Pearson Square to Blend Wines

Here’s an example of how this works. Let’s say we’ve got a 15% ABV wine and a 10% ABV wine. Our goal is to blend these two wines together to produce 6 gallons of wine that has an alcohol content of 13.5%.

Here’s how it lays out in the Pearson Square.

Blending Wines Using Pearson's Square

The vertical lines “||” are the symbol for absolute value in case your algebra is rusty. So even though B – C is a negative number take it as positive for the purposes of this calculation.

You may have noticed that the units for D and E are labeled as “parts”. Mixing 3.5 parts of wine A with 1.5 parts of wine B will result in a final alcohol content of 13.5%.

To get these quantities into units of measurement that are actually useful we can calculate the percentage of each as follows:



Just to be sure we did this correctly we can add the volume of wines A and B together and we get a total of 6 gallons. Hooray!

Please note that Pearson’s Square and the equations presented here are not specific to the English system of units. You may use liters, tons, tonnes, barrels, teaspoons, etc.

You can also use this tool in a slightly different way. For example, if you have six gallons of Merlot with a titratable acidity (TA) of 6.5 and you want to know how much Syrah to mix with it to bring your titratable acidity to 5.9 knowing that it the Syrah has a titratable acidity of 5.0 you can use the square like this:

Example of using Pearson's Square to blend wines of different titratable acidity.

Rules for Using Pearson’s Square

Now that you understand how it works there are a couple rules to keep in mind. If you break these rules the Pearson Square will give you strange results.

Rule #1: The value of C must be between A and B.

This makes sense. If you have a 15% ABV wine and a 10% wine you can blend the two to produce a final blend with and an alcohol content anywhere between these two concentrations. You cannot blend a 15% and 10% ABV wines and wind up with an 18% wine. It just doesn’t work.

Rule #2: D and E are always taken as positive values.

We’re concerned with the difference between A and C as well as B and C. Disregard and negative results and take them as positive numbers.

Final Thoughts

That was quite a bit of math. Once you’ve done it once or twice though you’ll start to see the simplicity of it. The alternative is solving simultaneous equations which won’t be simple at all.

I highly recommend running through any calculations at least twice before you begin mixing your wines. You don’t want to find a mistake in your math after you’ve already blended your wines. At that point you’re kind of stuck.

Photograph by: Maureen Didde