# Is Diet Coke 99% water?

I've come across the claim a few times that Diet Coke is 99% water.

Examples:

Partial support for the claim seems to stem from the following advertisement, which seems to imply there is no major difference between Diet Coke and water.

Is this claim accurate?

• I would think that just about any soft drink is at least 98% water by volume, but the 2% makes a difference— just like the 2% of DNA that separates humans and chimpanzees. Nov 16, 2012 at 5:25
• @Choster I don't find it hard to believe that they are mostly water, but I've encountered a lot of people who disagree, so am looking for some solid proof either way. Nov 16, 2012 at 5:44
• @Sklivvz What was wrong with the image? Nov 16, 2012 at 16:13
• @SonnyOrdell it was an ad, but it didn't add to the question because it was not the ad in question! :-P There's a "99%" ad which would be relevant, but the ad you put in was just a random Coca-Cola ad. Nov 16, 2012 at 16:16
• Maybe we could do a new question: Does the 99% water ad exist? Because - I can't find it, either. Nov 16, 2012 at 19:25

## 1 Answer

TL,DR: Diet cola is 99.8% water. Normal cola is 90% water and (basically) 10% sugar.

The claim is not correct, however in my opinion when someone claims "A is 99% B" they may not mean that literally. In particular the Freakanomics article works with any other ratio in mind - the article is about how claiming that something is mostly water has actually become a good thing and that relates to the price of water.

According to the USDA data:

Some notes:

1. The Coca-Cola company sells syrup which is then diluted in order to make the beverage. The dilution varies on a case-by-case basis, within some acceptable parameters. See for example here for a suggested soda fountain setting. This means that the percentage of water is variable, depending on the sample.

2. There is a big difference between 99% and 99.8% of water. There is five times more syrup (or "taste") in a 99% dilution than in a 99.8% dilution . 99% means 1g every 100g of liquid; 99.8% means 1g every 500g.

3. The USDA data is meant to be a standard reference - you can check the links above - given they provide 4 significant digits in the measurement, I doubt that there's more than 1% error in the values. This would include making sure the sample is representative.

• As a side note (or homework left to the reader), you can also do your chemistry calculations based on syrup composition and dilution ratio. I trust the chemists of USDA to give a more precise result, though, hence the comment. Nov 16, 2012 at 9:23
• Diet cola is 99.8% water would indicate that the claim is indeed correct, right? Nov 16, 2012 at 15:29
• @ste It would indicate that it's off by 0.8%. Nov 16, 2012 at 16:12
• I understand that as meaning at least 99% but not 100%. Nov 16, 2012 at 16:19
• @Stefan I agree, and in fact I specifically say "in my opinion when someone claims "A is 99% B" they may not mean that literally" Nov 16, 2012 at 16:23