Daily Water Intake Calculator
Find out how much water you should drink each day based on your body weight, exercise habits, climate, and special conditions like pregnancy. Use it to stay properly hydrated and avoid fatigue or dehydration.
About this calculator
Your daily water requirement isn't one-size-fits-all — it depends on body mass, physical activity, environmental heat, and physiological state. The base recommendation is roughly 35 mL of water per kilogram of body weight. Exercise adds demand: each hour of activity adds approximately 1,000 mL (1 litre) to cover sweat losses. Climate multipliers account for hot or humid environments where you lose more fluid through perspiration. Special conditions such as pregnancy or breastfeeding further increase needs. The formula used here is: Water (mL) = ((weight × 35) + (activityHours × 1000)) × climateFactor × conditionFactor. All four inputs combine to give a personalised daily target in millilitres.
How to use
Suppose you weigh 70 kg, exercise for 1 hour per day, live in a hot climate (factor 1.2), and have no special conditions (factor 1.0). Step 1 — base intake: 70 × 35 = 2,450 mL. Step 2 — add activity: 2,450 + (1 × 1,000) = 3,450 mL. Step 3 — apply climate factor: 3,450 × 1.2 = 4,140 mL. Step 4 — apply condition factor: 4,140 × 1.0 = 4,140 mL per day, or about 4.1 litres. That is your personalised daily water target.
Frequently asked questions
How much water should I drink per day based on my weight?
A widely used guideline is 35 mL of water per kilogram of body weight as a baseline. For a 60 kg person that works out to 2,100 mL (2.1 litres) before accounting for exercise or climate. Heavier individuals have larger muscle mass and metabolic output, so their absolute needs are higher. This calculator applies that 35 mL/kg baseline and then layers on additional factors for a more accurate personal target.
Why does exercise increase my daily water intake requirement?
During physical activity your muscles generate heat, and your body sweats to cool itself down. Sweat losses during moderate to vigorous exercise can easily reach 0.5–1.5 litres per hour. Failing to replace this fluid leads to dehydration, which impairs performance, concentration, and cardiovascular function. This calculator adds approximately 1,000 mL per hour of exercise to ensure those losses are covered.
When should pregnant or breastfeeding women drink more water?
Pregnancy increases blood volume and amniotic fluid needs, raising daily water requirements by roughly 300 mL above normal. Breastfeeding adds even more demand — typically an extra 700–1,000 mL per day — because breast milk is about 87% water. Inadequate hydration during these periods can affect milk supply, nutrient delivery to the baby, and maternal energy levels. The special conditions multiplier in this calculator adjusts the total upward to reflect those elevated physiological needs.