Last updated: Jun 25, 2024

SO2 Wine Calculator

Q: How do I add SO2 to wine?

To add sulfur dioxide (SO 2 ) to wine, you can: Add sodium metabisulphite powder; Add Campden tablets (it is actually the same as sodium metabisulphite); Use potassium metabisulphite tablets or powder — most common method ; or Theoretically, you can also inject SO 2 as a pure gas into your wine. This method is mostly used by commercial wineries.

Q: How much molecular SO2 is in a wine with a free SO2 of 24 mg/L, and a pH of 3.6?

The content of molecular SO 2 in this wine is 0.383 mg/L. To count this on your own: Measure the content of molecular SO 2 in your wine. Measure the pH. Solve the equation: molecular SO2 = free (measured) SO2/(1+10^(ph-1.81)) The answer is 0.383 mg/L.

Q: How much molecular SO2 should be in my wine?

The recommended level of molecular SO 2 is: 0.5 mg/L (ppm) for red wines; 0.8 mg/L (ppm) for white wines; and Up to 1.5 mg/L (ppm) for dessert wines. ppm — parts per million

Created by Aleksandra Zając, MD

Aleksandra Zając

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A young Medical Doctor certified International Board of Lifestyle Medicine Diplomate. In one of the big Warsaw clinics, she's responsible for prophylaxis and medical education. Professionally interested in nutrition, exercise, and mental health. She wants never to stop learning and currently studies postgraduate psychodietetics. She likes to bake and play with her pets – one dog and four fancy mice. See full profile

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Reviewed by Purnima Singh, PhD and Adena Benn

Adena Benn

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Adena Benn is an Information Technology teacher with a degree in Computer Science. She has been teaching high schoolers since 1996 and loves everything computers. She loves problem-solving, so creating calculators to solve real-world problems is her idea of fun. She writes children's stories, is a seamstress, and is an avid reader. In her spare time, she travels and enjoys nature. See full profile

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Table of contents

Effects of sulfites in wine — why are sulfites added to wine?Calculating molecular SO2 in wine Using the SO2 wine calculator Are sulfites bad for your health?FAQs

If you're about to make your own wine at home, the SO₂ wine calculator might be handy!

Read on to learn about calculating molecular SO₂ in wine, the effects of sulfites in wine, and how you manage to add SO₂ to wine.

Have you ever wondered whether sulfites are bad for your health? We've covered that, too!

Don't forget to check out as well:

The alcohol dilution calculator; and
Alcohol by volume calculator.

Effects of sulfites in wine — why are sulfites added to wine?

Why would you even want to use a SO₂ wine calculator? To count the right amount of sulfites to add to your wine, of course. But why add them at all?

Effects of sulfites in wine include:

They inhibit the growth of bacteria (including acetic bacteria, guilty of the vinegar taste);
They prevent the growth of wild yeast;
They keep wine fresher;
They keep the right color — prevents the wine from browning; and
They allow the wine to last longer in storage.

Sulfites occur naturally in most wines. They're a product of yeast fermentation. However, yeast produces only a minimal amount of sulfites — that's why winemakers often add more, so they can act as preservatives in wine.

Calculating molecular SO2 in wine

When added to wine, SO₂ (sulfur dioxide) can become a few things:

A diagram showing how SO2 behaves when added to wine.

The molecular form of SO₂ is the actual preserving, microbial-fighting agent. This is what adding SO₂ to wine is about! You can't measure molecular SO₂ directly, but you can count it if you know the pH and free SO₂ content of your wine.

The pH could be measured with pH meter or pH test strips;
Free SO₂ can be measured in a wine laboratory or at home, using, for example, test kits.

Once you've got your values, simply solve the equation:

\small \rm mol.\ SO_2 = \frac{\rm free\ SO_2}{1+10^{(pH-1.81)}}

where:

$\rm mol.\ SO_2$ — Molecular SO₂,
$\rm free\ SO_2$ — Free (measured) SO₂.

On the other hand, if you want to know how much free SO₂ you need to achieve to get the desired molecular SO₂, use the formula:

\small \rm RFSO_2=DSO_2 × (1 + 10^{(pH-1.81)})

where:

$\rm RFSO_2$ — Required free SO₂,
$\rm DSO_2$ — Desired molecular SO₂.

Remember you can always use our SO₂ wine calculator instead. 😉

Using the SO2 wine calculator

Use the SO₂ wine calculator to determine how much molecular SO₂ (sulfur dioxide) there is in your homemade wine. The first rows of the calculator are all about calculating molecular SO₂ in wine. The lower part counts where you should aim for while adding SO₂ to wine. Now follow the steps:

Fill in the calculator with the current Free SO₂ level.
Enter the wine pH.
You'll see the current content of the molecular count SO2 immediately.
The molecular SO2 level is the actual working agent in our homemade wine. That's why its level is so important. Fill in the row of Desired molecular SO₂ — those levels depend on the kind of wine you're making. Hover over that row to see the help text on this.
After typing in the desired molecular SO₂, you'll immediately see what level of Free SO₂ you should aim for.

Are sulfites bad for your health?

So you might have been repelled by those 'Contains sulfites' labels on the wine bottles. But should you be concerned?

First, we must look at the difference between sulfites and sulfates. They are not the same! Sulfites are food preservatives, and you will find them in many food products, not only wines. Adding SO₂ (sulfur dioxide) to wine will prevent it from spoiling. Sulfates, on the other hand, are strong detergents and used as cleaning agents. Do you recall SLS (sodium lauryl sulfate) from your shampoo? It is an example of sulfate as well.

Regarding health issues, sulfites are generally safe to eat, while sulfates are certainly not. However, certain people might be affected even by a small amount of edible sulfites. Usually, it's the case of persons with asthma, allergies, or a history of anaphylaxis reaction.

Summing up: If you're not sensitive to sulfites, they are relatively safe for your health.

FAQs

How do I add SO2 to wine?

To add sulfur dioxide (SO₂) to wine, you can:

Add sodium metabisulphite powder;
Add Campden tablets (it is actually the same as sodium metabisulphite);
Use potassium metabisulphite tablets or powder — most common method; or
Theoretically, you can also inject SO₂ as a pure gas into your wine. This method is mostly used by commercial wineries.

How much molecular SO2 is in a wine with a free SO2 of 24 mg/L, and a pH of 3.6?

The content of molecular SO₂ in this wine is 0.383 mg/L.

To count this on your own:

Measure the content of molecular SO₂ in your wine.
Measure the pH.
Solve the equation:

molecular SO2 = free (measured) SO2/(1+10^(ph-1.81))
The answer is 0.383 mg/L.

How much molecular SO2 should be in my wine?

The recommended level of molecular SO₂ is:

0.5 mg/L (ppm) for red wines;
0.8 mg/L (ppm) for white wines; and
Up to 1.5 mg/L (ppm) for dessert wines.

ppm — parts per million

Do all wines have sulfites?

Most wines contain sulfites, but you still can find wines without them. Yeast produces sulfites during the process of wine fermentation. Sometimes, winemakers add more sulfites (or sulfur dioxide — SO₂) to the beverage. In the right amount, they act as preservatives in wine.