For a while, I've been under the impression that the caffeine ration of soda:tea:coffee is roughly 1:2:4, but what are the actual numbers? Here are a couple of web sites that help answer that.
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first web site basically shows that caffenated sodas are about 25 to 50 mg per 12oz can. Tea is about 50mg per 8 oz, and coffee more than 100mg per 8 oz. There is some variability.
The
second web site gives more details, but isn't great for direct comparisons.