TIL Starbucks coffee has a ton of caffeine. This explains why I'm super jittery every time I get Starbucks even though I drink (non-Starbucks) coffee every day.

So yeah, two freaking massive 20oz pours of highly caffeinated coffee will get you to around 1 gram.

But FWIW the daily recommended dose is 400mg. 1g is a ton of caffeine and way beyond what you would get to by sipping on coffee throughout the day (it's 10+ cups of drip).

I don’t know where you got 400mg/day. Last I checked it’s 160 mg/day.

https://health.gov/dietaryguidelines/2015 mentions that 400mg/day is the upper bound for moderate caffeine consumption but provides no citation.

I cannot find where the number originates, but there is at least one study @ https://www.sciencedirect.com/science/article/pii/S027869151... which explicitly claims "vidence supported consumption of ≤400 mg/day in adults is not associated with overt, adverse effects."