Water intake
How much water should you drink a day?
A range, not a rule. Enter your weight and how active today is; the answer comes out in glasses, litres and ounces, and everything you drink counts toward it.
An estimate from body weight and activity, not a prescription. Thirst and pale-yellow urine are the everyday signals. If a doctor has given you a fluid target, theirs wins.
Where the numbers come from
The U.S. National Academies set an adequate intake of about 2.7 litres of total water a day for women and 3.7 litres for men, and note that roughly 20 percent of that arrives in food. Those figures are averages for healthy adults in temperate climates, which is why a fixed number fits few people well. The calculator uses a common per-kilogram range of 30 to 35 millilitres, adds about 350 millilitres for every half hour of activity, and lifts the range on hot days. It is an estimate for a normal day, and a fluid target from your doctor always outranks it.
What counts
- Water, sparkling water, tea and coffee all count. Caffeine's effect on fluid balance is minor at everyday intakes.
- Milk, juice and soup count too, though the sugar in juice and soda is a separate question.
- Food matters: fruit, vegetables, yoghurt and cooked grains carry a surprising share of the day's water.
- Alcohol does not help. It increases fluid loss.
How to actually drink more
The people who hit their number rarely do it by willpower. They put a glass where the day already happens: one on the nightstand for the morning, one on the desk, one with each meal. Counting glasses turns out to matter more than the size of the glasses, because a count is a habit and a volume is a chore. That is the logic behind Orbit's water tool: tap once per glass, watch the glass fill, and let the day's count carry the habit.
Questions people ask
Does coffee count toward my water intake?
Yes. Coffee, tea, milk and other drinks all count toward total water. Caffeine's diuretic effect is small at normal intakes and does not cancel the fluid.
Is eight glasses a day a real rule?
It is a memorable round number, not a finding. Needs vary with body size, activity and heat, and about a fifth of daily water comes from food. The estimate above is a range for a reason.
How do I know if I am drinking enough?
Thirst and urine colour are the everyday signals: pale yellow is the usual sign of enough. Dark yellow, headaches and fatigue on a hot or active day are reasons to drink more.