Hydration, measured
What actually hydrates you
This is the part of the site that deals in measurements rather than advice. Everything below comes from published trials and USDA FoodData Central rather than from other websites: how much fluid 13 drinks actually held on to against still water, how much water is in the food on your plate, and what each glass costs you in sugar, caffeine and calories. Every number carries a reference you can open, and where the evidence is thin, narrow or paid for by a drinks company, the page says so instead of rounding it into a ranking.1,2
Last reviewed 3 sourcesWritten from the studies, not from other websites
Start here
The two data pages
One for what you drink, one for what you eat. Both are built from the same evidence, and both show their working.
- DrinksThe most hydrating drinks, measured
Every drink from the trial that created the beverage hydration index, ranked against still water, with what each glass carries in sugar, caffeine and calories.13 drinks1,2Measured against still water in one trial of 72 men, alongside the 23 drinks the hub covers.Open the data - FoodsHow much water is in your food?
Water content per portion for everyday foods, in millilitres rather than percentages, plus what food water does and does not replace.32 foods2,3Water per portion in millilitres, and why about a fifth of your daily water arrives as food.Open the data
Drink by drink
The questions people actually ask
Four drinks with enough measured data to answer properly. Coffee, tea and sparkling water are answered in the guides further down rather than twice.
MilkDoes milk hydrate you?The one everyday drink that beat water by a clear margin, and the window where that holds.1.581Skim milk's 2-hour index against water's 1.00; whole milk scored 1.50.Read the answer
Sports drinksDoes Gatorade hydrate you?What a sports drink does at rest, what it is actually formulated for, and when it is worth the sugar.1.021A sports drink drunk at rest, which was not measurably different from water.Read the answer
SodaDoes soda hydrate you?Cola and diet cola against water, and why a drink can hydrate you and still be a poor daily habit.1.231Cola scored above water on average, but not by enough to call it a difference.Read the answer
JuiceDoes orange juice hydrate you?Juice looked better than water until the maths was corrected for its own water content.1.391Orange juice beat water until the index was corrected for its own water content, at 1.24.Read the answer
The honest part
What this evidence is, and is not
Four things worth knowing before you read any of it.
It measures two to four hours, not a day
The beverage hydration index is one number: urine after a litre of still water divided by urine after a litre of the test drink, two hours after drinking ended. It was measured in 72 rested, already-hydrated men aged 18 to 35 who drank each litre in 30 minutes. Nothing here has followed a drink across a full 24 hours.1
Water is the baseline, and most drinks match it
Only the two milks and an oral rehydration solution stayed above water once each drink was corrected for its own water content. Coffee at 0.91, tea, cola and a sports drink were all statistically indistinguishable from it. "As good as water" is the usual answer, and it is a perfectly good one.1
Food counts, and by more than people expect
NASEM puts about 19 to 20% of total water intake at food rather than drinks, which is why there is a foods page here at all. It is a real contribution, not a trick for skipping the glass.3
Composition is USDA's, converted, never typed by hand
Every per-glass and per-portion figure is built from USDA FoodData Central's published per-100-gram values, converted through each item's density. Where a study was industry funded, the reference says who paid. Where the evidence does not exist, the page says that instead of guessing.2
Free tools
- Water intake calculatorYour daily target from weight, activity, climate and altitude — shown in ounces, millilitres, litres, cups and bottles at once.
- Caffeine calculatorHow much caffeine is still in you at bedtime, drawn as a decay curve — plus where you are against the daily limit.
- Sweat rate calculatorWeigh in, train, weigh out. Get your litres-per-hour, your fluid deficit, and how much to drink per hour next time.
- Hydration colour chartTap the shade that matches. Get a plain reading and how much to drink to correct it.
Related reading
- How to hydrate fasterWhat to do when you are already behind, rather than what to drink day to day.
- Does coffee count towards water intake?The measured answer for the drink most people have before their first glass of water.
- Does tea count as water intake?Hot, iced and the caffeine question, handled separately from the hub.
- Does sparkling water hydrate you?What the bubbles do, which is less than most people assume.
Receipts
Where these numbers come from
Each page under /hydration carries its own full reference list. These are the sources behind the numbers on this page.
Who paid for the research
Hydration research is heavily industry funded. That does not make a study wrong, but you should know who paid before you weigh it. Water Goose took no money from anyone named here.
- — Maughan 2016: Funded by a grant from the European Hydration Institute (EHI). Prof Maughan chairs the EHI Scientific Advisory Board (not the Institute itself); Dr Watson has also received EHI funding.
- 1
Maughan RJ, Watson P, Cordery PAA, Walsh NP, Oliver SJ, Dolci A, Rodriguez-Sanchez N, Galloway SDR. A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index. Am J Clin Nutr 2016;103(3):717-723.
StudyRead: full textOpen source
Funding: Funded by a grant from the European Hydration Institute (EHI). Prof Maughan chairs the EHI Scientific Advisory Board (not the Institute itself); Dr Watson has also received EHI funding.
Read from the LJMU green open-access accepted manuscript (https://researchonline.ljmu.ac.uk/id/eprint/12468/); the publisher page was blocked. ISRCTN13014105.
- 2
U.S. Department of Agriculture, Agricultural Research Service. FoodData Central (SR Legacy and Foundation Foods).
DatasetRead: official pageOpen source
Water content is not the same thing as a net hydration effect.
- 3
Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Chapter 4: Water. Washington, DC: The National Academies Press; 2005.
GuidelineRead: full textOpen source
Cite this directly for adequate intakes: Maughan 2016's introduction misstates the women's figure. On alcohol it concludes the diuresis is transient; it makes no explicit 'all drinks count equally' statement.
These pages describe what studies measured in healthy adults. It is general wellness information, not medical advice, diagnosis or treatment. Fluid needs change with health conditions, medication and pregnancy — and some conditions require drinking less. Talk to a clinician about yours.
Keep the number
This section can tell you which drinks hold water and which only look like they do. Water Goose is what remembers you drank them — every drink at full volume, no multipliers.
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