Water Intake Calculator
Gives a general estimate of how much to drink each day.
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The formula
total = 30 ml × kg + exercise hours × 0.5 to 1 L drinks = total × 0.8
About a fifth of the water you take in usually comes from food, so that share is taken off.
What to watch out for
30 ml per kg is a common rule of thumb, not a measured requirement. EFSA (2010) sets adequate total water at 2.0 L a day for women and 2.5 L for men. Food usually supplies about 20–30% of water intake. The NHS suggests 6–8 glasses of fluid a day. Sweat losses during exercise vary widely: the American College of Sports Medicine (2007) gives about 0.5–2 L an hour, and the figures here sit at the low end of that.
Frequently Asked Questions
How much water should I drink a day?
For 70 kg with 30 minutes of moderate exercise, about 2.0 L of drinks a day, or 8 glasses.
How can I tell if I am drinking enough?
Thirst is a good guide for most healthy adults, and pale straw-coloured urine usually means you are well hydrated.
Do tea and coffee count?
Yes, according to the NHS. Water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count.