The Short Answer
Almost everything you drink contributes to your daily fluid intake to some degree — but not all beverages hydrate equally well. Caffeinated and alcoholic drinks have a mild diuretic effect, meaning they increase fluid loss slightly and so contribute less net hydration per millilitre than plain water.
Beverage-by-Beverage Breakdown
| Drink | Hydration Value | Notes |
|---|---|---|
| Water | Full | The baseline reference — no adjustment needed |
| Herbal Tea | Full | Caffeine-free, hydrates similarly to water |
| Milk | Full or near-full | High water content, plus electrolytes |
| Coffee / Caffeinated Tea | Slightly reduced | Mild diuretic effect, but still net-positive for hydration |
| Juice | Reduced | Hydrating, but high sugar content should be considered |
| Soda | Reduced | Similar to juice — hydrating but sugar-heavy |
| Alcoholic Drinks | Significantly reduced | Notable diuretic effect — can contribute to net fluid loss |
This is the same logic used in the Daily Fluid Log on our Liquid Intake Calculator — each drink type carries a hydration multiplier reflecting how much it really contributes toward your target, not just its raw volume.
Does Coffee Really Dehydrate You?
This is one of the most persistent hydration myths. In moderate amounts, coffee and caffeinated tea are still net-positive for hydration — the mild diuretic effect doesn't cancel out the fluid you're drinking, it just slightly reduces how much of it "counts." Habitual coffee drinkers also tend to develop some tolerance to caffeine's diuretic effect over time.
What About Alcohol?
Alcohol has a more pronounced diuretic effect than caffeine, increasing fluid loss through increased urination. This is why alcoholic drinks contribute much less net hydration than their volume suggests — and why it's commonly recommended to drink water alongside alcohol to help offset the loss.
Does Food Count Toward Hydration Too?
Yes — roughly 20% of daily fluid intake typically comes from food rather than drinks, especially water-rich foods like fruits, vegetables and soups. This is a natural buffer on top of your beverage intake, which is one reason calculators (including ours) estimate targets from beverages specifically, leaving some margin from food.
Practical Takeaway
- Water, herbal tea and milk hydrate at close to full value — drink these freely toward your target.
- Coffee and caffeinated tea still count, just slightly less than their raw volume.
- Juice and soda hydrate, but their sugar content is worth considering separately from hydration.
- Alcohol contributes the least net hydration and can accelerate fluid loss — pair it with water.
Rather than mentally adjusting for all of this, log your actual drinks in the Daily Fluid Log below and let the hydration multipliers do the maths for you.