# Does black coffee count as water?

It does, and the app counts every millilitre of it. Why coffee is not the dehydrator it is said to be, and how long a 95 mg cup stays with you.

## Numbers the app uses

| Field | Value |
| --- | --- |
| Default serving | 240 ml |
| Hydration factor | 1.00 |
| Counts toward the daily goal | 240 ml per serving |
| Caffeine | 95 mg per serving |
| Calories | 1 kcal per 100 ml (2 kcal per serving) |

## The whole cup counts

Black coffee sits at a hydration factor of 1.00, level with water. A 240 ml cup adds 240 ml to the day. That is not a generous rounding. Researchers compared drinks head to head for how much of each the body held on to. Coffee finished in the group that matched still water. The trial is cited at the foot of this page. Caffeine does nudge the kidneys. At the dose in an ordinary cup, the water arriving covers the water leaving. Habitual drinkers show less of the effect than occasional ones.

## Weaker to taste, stronger in the cup

A 240 ml cup of black coffee is 95 mg of caffeine, half again as much as an espresso shot. The espresso is the one that tastes like it means it. The reason is arithmetic rather than chemistry. A filter cup uses more ground coffee, and far more water passes through it. More caffeine ends up dissolved, even though ten times the volume thins it. Two cups put you around 190 mg, which is roughly where a single sitting stops being small.

## Where the 95 milligrams is at bedtime

Caffeine leaves slowly. On a typical five-hour half-life, a 95 mg cup at four in the afternoon still leaves about 40 mg circulating at eleven at night. That is near enough a cup of green tea, arriving at the worst possible moment. The app draws that curve rather than assuming the coffee is gone. When the sums stop working, every coffee in the app has a **Decaf** switch. It logs the water and the calories and records the caffeine as zero. On teas the same switch reads *Caffeine-free*.

## Source

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. https://pubmed.ncbi.nlm.nih.gov/26702122/

Page: https://waterchamp.app/drinks/black-coffee/