Daily Water Intake by Body Weight Calculator
Calculate your recommended daily water intake based on your body weight and activity level.
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Enter your values and click Calculate
How It Works
Base ounces = body weight (lbs) ÷ 2. This gives the minimum daily recommendation for a sedentary person at a neutral temperature. Activity level adds a fixed number of ounces on top: 0 oz for sedentary, 8 oz for light (1–3 days/week), 16 oz for moderate (3–5 days/week), 24 oz for active (6–7 days/week), and 32 oz for very active (twice-daily training). Total oz = base oz + activity oz. Liters = total oz × 0.02957 (the number of liters per fluid ounce). Cups = total oz ÷ 8, since one US cup equals 8 fluid ounces. The base figure is also displayed separately so you can see the activity contribution clearly.
Examples
Moderately active person
160 lbs, moderate activity (3–5 days/week).
Result: Base 80 oz + 16 oz activity = 96 oz (2.84 liters, 12 cups).
Sedentary person
140 lbs, little to no exercise.
Result: 70 oz (2.07 liters, ~8.75 cups).
Very active athlete
200 lbs, training twice daily.
Result: Base 100 oz + 32 oz activity = 132 oz (3.90 liters, 16.5 cups).
Frequently Asked Questions
Is the half-your-weight formula accurate?
It is a well-known practical estimate, not a clinical prescription. Individual needs vary significantly with climate, altitude, health conditions, and diet — foods with high water content like fruits and vegetables reduce how much you need to drink. Use the result as a target range rather than a precise requirement.
Can I drink too much water?
Yes, though overhydration (hyponatremia) is rare outside of endurance sports. Drinking far more than your body needs can dilute blood sodium to dangerous levels. Stick to ranges produced by this calculator and consult a doctor if you have kidney disease or other conditions affecting fluid balance.
Why are the activity additions fixed amounts rather than percentages?
Fixed ounce additions (8–32 oz) are a practical approximation for sweat replacement during exercise. The actual amount lost varies with temperature, humidity, and sweat rate, but these values are widely used as reasonable general guidelines for everyday hydration planning.