Matt Holden

Espresso/short black coffee.
Surprised? A short black contains less caffeine than Red Bull. Photo: Marco Del Grande

Pop quiz: Which has more caffeine - a can of Red Bull or a chainstore short black?

The energy drink just pips the espresso, with 80 milligrams of caffeine to 75 milligrams in a single Starbucks-style espresso. A cup of drip-filter coffee tops them both, with 145 milligrams.

The Up Coffee app uses data about your height, gender, weight and sensitivity to caffeine to calculate how quickly your body metabolises it.
The Up Coffee app uses data about your height, gender, weight and sensitivity to caffeine to calculate how quickly your body metabolises it.

That's according to data from a United States Food and Drug Administration report, Caffeine Intake by the US Population.

And what about all your office colleagues drinking endless cups of tea? How do they fare in the jitter stakes? A one-minute brew of generic black tea contains about two-thirds as much caffeine as an espresso. Let it stew for five minutes and it almost matches.

So how much caffeine is too much?

According to some, the answer is: "There's no such thing!!!" (That triple exclamation mark is an emoticon that signifies "overcaffeinated".)

But Victoria's Better Health website says up to 500 milligrams of caffeine a day is OK, although it obviously depends on your body mass, whether or not you're pregnant, and other physiological factors.

The website has higher estimates of the caffeine content of beverages: 150-200 milligrams for espresso. Two or three espressos a day are OK with those figures, while the Australian Drug Foundation classifies four cups of coffee a day as "moderate intake" - depending on the brew.

If keeping track of how much you've had is too hard (short-term effect of caffeine consumption - increased concentration; overdose effect - confusion), there's a new app that will do it for you - and it will estimate when you should be ready for bed based on what you've had.

The app, Up Coffee, uses data about your weight, height, gender and sensitivity to caffeine (not, somewhat or very sensitive) to calculate how quickly your body metabolises it. Whenever you have coffee (or any caffeinated food or drink), you punch the time and the drink into the app. A cute graphic of a laboratory flask fills with dancing bubbles that indicate your caffeination level - from "sleep ready" (low) to "wired" (too much coffee, man!!!). A dial indicates whether you should be feeling calm, OK or edgy, while a bar graph shows how your caffeine levels will rise and fall during the day based on your consumption.

If you want to get more scientific, pair the app with the Up wristband, which tracks activity - including sleep, exercise and whether you've been sitting still for too long at a screen - and synchs the data wirelessly with smartphone apps to help you track the effect of food, drink and other activities on your mood.

But that could just be too much information, man!!!