Water Intake Calculator
A daily water target based on your body weight and exercise time.
How it works
ounces = weight(lb) × 0.5 + 12 oz per 30 min of exercise
A widely used practical rule: half your body weight in fluid ounces as a base, plus about 12 oz per half hour of sweaty activity. It approximates institute guidance (roughly 3.7 L/day total water for men, 2.7 L for women, food included) scaled to body size.
Worked example
At 170 lb with 45 minutes of training: 85 oz base + 18 oz exercise ≈ 103 fl oz — about 13 cups or 3 liters.
Frequently asked questions
Does coffee count?
Yes. Caffeinated drinks are mildly diuretic but still net-hydrating; regular drinkers adapt further.
Can I drink too much water?
Yes — drinking many liters rapidly can dilute blood sodium (hyponatremia), a real risk in endurance events. Spread intake out and salt normally.
Do I need electrolyte drinks?
Mostly only for sessions over ~60–90 minutes of heavy sweating or hot conditions; normal meals replace typical losses.
Related calculators
This is a general educational estimate, not medical advice. Bodies differ — for decisions about diet, training, medication or health conditions, talk to a doctor or registered dietitian.