Daily Water Intake Calculator
Water Intake Calculator
Adequate hydration supports every system in the body — from regulating temperature and transporting nutrients to lubricating joints and flushing waste. Your ideal water intake depends on body size, activity level, climate, and overall health. This calculator gives a science-backed starting point.
Conversion Formula
The base formula multiplies body weight in kilograms by 0.033 liters to get a resting daily requirement. An activity multiplier (1.0 to 1.8) scales the result upward for more active lifestyles.
Step-by-Step Examples
170 lbs (77 kg), Sedentary, imperial = 2.5 liters / 86 fl oz / 10.8 cups
77 × 0.033 × 1.0 = 2.54 liters; × 33.814 = 85.9 fl oz; / 8 = 10.7 cups
85 kg, Very Active, metric = 4.5 liters / 151 fl oz / 18.9 cups
85 × 0.033 × 1.6 = 4.49 liters; × 33.814 = 151.8 fl oz; / 8 = 19.0 cups
Frequently Asked Questions
How much water should I drink per day?
A common guideline is about 0.033 liters (1.1 fl oz) per kilogram of body weight per day at rest. For a 77 kg (170 lb) sedentary person, that is about 2.5 liters (85 fl oz / ~10.5 cups). Active individuals need significantly more — a 77 kg person doing intense daily training may need 4+ liters per day.
Does coffee, tea, or juice count toward my daily water intake?
Yes, all beverages contribute to total fluid intake. Plain water is the best choice, but coffee, tea, milk, and juice all count. Caffeinated drinks have a mild diuretic effect but still provide net hydration at moderate amounts. Alcohol is dehydrating and does not count positively.
How do I know if I am drinking enough water?
The simplest indicator is urine color. Pale yellow (like lemonade) means well-hydrated. Dark yellow or amber means you need more water. Clear urine may mean you are over-hydrating. Other signs of dehydration include thirst, dry mouth, headache, and reduced urine output.