New
BMI Calculator
Body Mass Index with WHO classification and healthy weight range.
CostNest Calculator
Water Intake Calculator
Daily water intake by weight, activity and climate. No signup — your inputs stay in your browser.
Step By Step
How to Use This Calculator
4 steps
- Enter your body weight in kg or lbs.
- Pick the activity level that matches your typical day — sedentary means mostly sitting, extreme means hard training daily.
- Choose your usual climate — 'Very Hot (BD summer)' adds extra for heat and humidity.
- Tick Pregnant or Breastfeeding if relevant. Your daily fluid target updates instantly.
Worked Example
Example: 65 kg, moderate activity, warm climate
Use this sample to sanity-check your inputs and understand what the final result represents.
- 1Base: 65 × 0.033 = 2.15 L
- 2Moderate activity: +0.35 L
- 3Warm climate: +0.30 L
- 4Total: 2.80 L per day
Final Result
≈ 11 glasses of 250 ml — counting all fluids, not just plain water.
Methodology
33 ml/kg base + activity, climate & condition adjustments
This section explains the calculation logic, assumptions, and source material used to make the result more trustworthy and easier to verify.
Base = weight (kg) × 0.033 L. Activity adds 0–1.0 L depending on exertion. Climate adds 0–0.70 L for heat and humidity. Pregnancy adds 0.3 L; breastfeeding adds 0.7 L per National Academy of Medicine guidelines (Dietary Reference Intakes, 2004). The result covers total fluid intake from all sources including food.
Frequently Asked Questions
Where does the 33 ml per kg figure come from?+
It's a widely used clinical rule of thumb for healthy adult hydration — roughly 1 ml per calorie of energy expenditure, which works out to around 30–35 ml/kg for most adults. The National Academy of Medicine sets general adequate intake at 3.7 L/day for men and 2.7 L/day for women (including food), but these are population averages. The per-kg formula is a more personalised starting point.
Does this count tea, coffee, and food — or just plain water?+
The result is total fluid intake from all sources. That includes water, tea, juice, dal, and the water content of fruits and vegetables — which typically contributes about 20% of daily fluid needs. You don't need to drink the entire amount as plain water.
Why is there an extra amount for breastfeeding?+
Breast milk is roughly 87% water, so producing it raises daily fluid needs significantly. The National Academy of Medicine recommends breastfeeding women consume about 3.1 L of total fluids per day — around 700 ml more than the average non-pregnant adult woman. This calculator adds 0.7 L to account for that.
How much extra water do I need in Dhaka's summer?+
The 'Very Hot' climate option adds 0.7 L to your base. In high humidity and heat, sweat losses can exceed 1–2 L per hour during outdoor activity, so this is a minimum adjustment. If you're working or exercising outside in peak summer, drink to thirst and watch for dark urine as a sign of dehydration.
Can I drink too much water?+
Yes, though it's rare in healthy adults. Overhydration (hyponatremia) happens when excess water dilutes sodium in the blood. It's mainly a risk for endurance athletes who drink large volumes without replacing electrolytes. For most people with normal kidney function, thirst is a reliable guide — this tool just gives a baseline target.
Does this work during Ramadan fasting hours?+
The daily total stays the same, but you'd spread your intake across iftar to suhoor. Prioritise water-rich foods and avoid sugary drinks that increase thirst. The hot climate adjustment is especially relevant during summer Ramadan.