Water Intake Calculator - Daily Hydration by Weight & Activity
Estimate how much water you should drink daily based on body weight and activity level. Get results in milliliters, liters, fluid ounces, and cups.
Your Details
Weight-based hydration with activity adjustment.
Daily Water Intake
Recommended Daily Intake
2,890 ml
2.9 liters · 12.3 cups
Methodology and limitations
Last reviewed:
Methodology
Calculates base daily fluid needs at 35 mL per kg body weight, then adds activity-based bonus volumes for moderate, high, and very-high activity levels.
Limitations
Hydration needs vary with climate, pregnancy, breastfeeding, illness, and medical conditions. Thirst and urine color are practical guides; people with kidney or heart conditions should follow clinician advice.
Official sources
How Daily Water Intake Is Estimated
Estimate how much water you should drink daily based on body weight and activity level. Get results in milliliters, liters, fluid ounces, and cups.
Method used
The calculator multiplies body weight in kilograms by 35 mL for a base daily fluid target, then adds activity-based bonus volume for moderate, high, or very-high exercise levels.
Total mL = (weight in kg × 35) + activity bonus; cups ≈ total oz ÷ 8
Practical example
A 160 lb (72.6 kg) person with moderate daily exercise might need about 2,540 mL base plus 350 mL activity bonus, totaling roughly 86 oz or 10.8 cups per day.
- Weight in pounds or kilograms
- Activity level from sedentary to athlete
The result shows base intake, activity bonus, total in mL, liters, ounces, and cups.
Assumptions
- Base formula uses 35 mL per kg body weight.
- Activity bonuses are fixed increments, not sweat-rate measurements.
- Total fluid includes water and other beverages unless your clinician advises otherwise.
What this includes
- Base hydration, activity bonus, total mL, liters, ounces, and cup equivalents.
What this excludes
- Pregnancy and breastfeeding needs, kidney disease fluid restrictions, climate-specific sweat losses, and electrolyte replacement planning.
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Frequently Asked Questions
How much water should I drink per day?
A common guideline is about 35 ml per kilogram of body weight, plus extra for exercise and heat. Individual needs vary with climate, diet (including watery foods), altitude, and health conditions. This calculator returns targets in milliliters, liters, fluid ounces, and cups. Pale yellow urine and stable energy are practical checks alongside the educational estimate.
Does coffee and tea count toward hydration?
Moderate caffeine intake still contributes to fluid balance for most healthy adults, contrary to the myth that coffee always dehydrates you. This calculator estimates total fluid needs; plain water remains the simplest way to meet them without extra sugar or caffeine. If caffeine worsens sleep or reflux, prioritize water and herbal options for most of your target.
How does activity change water needs?
Exercise increases sweat and respiratory water loss, especially in heat or high humidity. This calculator adds roughly 350–1,000 ml depending on activity intensity to your base weight-based estimate. Long outdoor sessions may need still more plus electrolytes when sweat loss is heavy. Increase gradually and sip across the day rather than chugging large volumes at once.
Can you drink too much water?
Excessive water intake in a short period can dilute blood sodium (hyponatremia), though this is uncommon in everyday settings. Spread intake across the day and increase gradually with heavy training instead of forcing extreme volumes. People with kidney, heart, or hormone conditions should follow clinician fluid guidance rather than generic online targets alone.
Do I need more water in hot weather?
Yes. Heat and humidity increase sweat loss, so thirst and urine color often signal higher needs outdoors or in non-air-conditioned spaces. Add extra fluids in hot climates or during outdoor workouts beyond what the standard activity bonus includes. Weighing before and after long hot workouts can roughly show fluid lost if you want a personal check.