Drink comparison
Drink Hydration Index calculator
Compare common drinks by simplified fluid-retention value. Useful for explaining why milk can retain more fluid than water, and why alcohol is not a hydration shortcut.
Hydration comparison
About 500 ml effective hydration
500 ml of water is roughly comparable to 500 ml on this simplified retention scale. Simple baseline.
Important limitation
This is an educational comparison inspired by Beverage Hydration Index research, not a clinical hydration measurement. Your daily default should still be water plus normal food.
Shareable stat card
Need the counterintuitive version for outreach or social? Use the milk hydration stat card and link it back to the full explanation.
Open milk hydration card
Frequently asked
Can milk hydrate better than water?
In Beverage Hydration Index research, milk retained more fluid than still water over the following hours, likely because electrolytes, protein, and lactose slow fluid loss.
Does coffee count as water?
Yes, coffee contributes fluid, especially for habitual caffeine users. Very large caffeine doses can be mildly diuretic, so water is still the cleaner default.
Does beer hydrate you?
Beer contains water, but alcohol suppresses vasopressin and increases urine output. It should not be used as a hydration strategy.