- Default serving40 mlCoffee
- Counts toward goal40 mlhydration factor 1.00
- Caffeine63 mgper 40 ml serving
- Calories1 kcal2 kcal per 100 ml
Move the slider to see what a bigger or smaller espresso does to the numbers. The app uses the same figures. The slider moves a shot at a time, which is how the app counts them.
See when today's caffeine clears with the caffeine cutoff calculator.
63 milligrams in 40 millilitres
A single shot carries 63 mg of caffeine in 40 ml of liquid. That works out at about 1.6 mg in every millilitre, roughly four times the concentration of filter coffee. A filter cup spreads its 95 mg across 240 ml. So espresso is the weaker drink measured by the cup and the far stronger one measured by the sip. People who say "I only had an espresso" are usually right about the caffeine and wrong about the reason.
The doubles are where it stops being a curiosity. The shot stepper in the app adds 40 ml and 63 mg for each extra shot. A double is 80 ml and 126 mg: more caffeine than a full mug of filter coffee, in a third of the liquid. For healthy adults, EFSA does not consider 400 mg a day, or 200 mg in one sitting, a safety concern (EFSA scientific opinion on caffeine, 2015). Three doubles reaches the daily figure before lunch.
What a shot does to the water goal
Espresso's hydration factor is 1.00, the same as water, so the app counts every millilitre in full. The problem is that there are hardly any millilitres. A shot puts 40 ml against a goal that usually sits somewhere near 2,000 ml. Fifty shots would cover a day. Espresso is a caffeine entry that happens to contain some water, and the app treats it that way.
Why the coffee deadline is measured in shots
The app's "last chance for coffee" reminder finds the latest moment one standard dose still fits. Drink it then and you stay under the sleep-safe caffeine level at your bedtime. That standard dose is 63 mg, one espresso shot. The unit is not decorative. Caffeine follows an absorption-and-elimination curve that peaks about one hour and fifty minutes after the drink. It peaks sooner if you metabolise it quickly, later if you do not. Drink a shot inside that window and the caffeine is still climbing while you try to fall asleep. That is the thing the reminder exists to head off.
Hydration factors follow the Beverage Hydration Index: Maughan RJ, Watson P, Cordery PA, et al. “A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.” American Journal of Clinical Nutrition, 2016;103(3):717-723. Read the paper on PubMed. In WaterChamp an espresso counts the same as plain water.
