A note on the submission title: I submitted the original title of webpage's mobile version (which includes the question "How Much Caffeine to Drink to Stay Alert?"), though the desktop version shortens the headline to just "Coffee Kick Calculator."
On how the model works, the authors mention on the webpage that: "The formula that we used in our calculator was developed by a team of scientists in the U.S. Army Medical Research and Materiel Command, Fort Detrick, Maryland. They described it in detail in the article titled A Unified Model of Performance for Predicting the Effects of Sleep and Caffeine." [1] I was searching for an interactive model of the study for a while, and I thought this website was a well-done way to visualize this.
A few limitations I found were that:
- By default, a cup of coffee is listed to contain about 150 mg of caffeine, whereas most other sources list the caffeine content as 100 mg (which significantly affects the model). The ability to change this isn't easy to discover at a first glance, but you can manually enter the caffeine amount by enabling the "Advanced" mode.
- The user interface will always include an extra "Caffeine drink" associated with a cup (or caffeine amount, if in advanced mode), but you can safely ignore this, as the last cup will not be recorded on the graph if the time amount is left blank. Similarly, to delete caffeine drinks, you can delete the recorded time for the most recent drink.
- The model assumes you drink a cup roughly all at one timepoint, and does not account for what happens if you sip a drink over time (though this have also been a limitation of the study that the software is based on).
- The model doesn't appear to account for tolerance to caffeine over time.
My takeaways are that: for alertness (without excessive alertness over time), it's better to wait at least an hour or two after waking up before a first caffeine drink. It's best to wait about 1-2 hours between each drink.
Anecdotally, the predicted alertness from the model also appears to hold true in my personal experience: on most days when I drink coffee, I've felt better drinking coffee spread out through the day, instead of a larger serving at once earlier in the morning.
I like coffee too, but drugs are unreliable attention modulators, compared to good food, plenty of rest, and a worthwhile goal.