💧 Dietitian-Approved Tool

Hydration Calculator

Find your personalized daily water intake goal based on your weight, activity level, and environment. Stay optimally hydrated for energy, metabolism, and performance.

Calculate Your Daily Water Needs

Enter your details for a personalized hydration target.

Weight (kg)

Activity Level

Climate / Environment

Pregnancy / Breastfeeding

Your Daily Water Goal

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litres per day

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8 oz Cups

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500 ml Bottles

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ml per Hour (16 hrs)

💡 Hydration Tips

Start your day with 1–2 glasses of water before coffee or food
Drink a glass of water before each meal to support digestion and satiety
Carry a reusable water bottle and refill it throughout the day
Foods like cucumbers, watermelon, and celery contribute to hydration
Urine color is a reliable indicator — aim for pale yellow
Increase intake during exercise, illness, hot weather, or pregnancy

Why Hydration Matters

Water makes up roughly 60% of the adult body and is involved in virtually every physiological process: nutrient transport, temperature regulation, joint lubrication, waste elimination, and cognitive function. Even mild dehydration (1–2% body weight) can impair concentration, mood, and exercise performance.

How Daily Water Needs Are Calculated

The most evidence-based approach uses body weight as the baseline:

Base formula: 35 ml × body weight (kg) per day
Example: 35 × 70 kg = 2,450 ml = 2.45 litres/day

Additional needs are added for activity level, climate, and physiological states like pregnancy and breastfeeding.

Factors That Increase Your Water Needs

Physical activity — you lose 0.5–2L per hour of exercise through sweat
Hot or humid weather — increases sweat rate significantly
High altitude — increased respiratory water loss
Pregnancy — plasma volume expands; ACOG recommends ~2.3L/day minimum
Breastfeeding — breast milk is ~87% water; needs increase by ~700ml/day
High-protein or high-fiber diets — both require more water for processing
Illness (fever, vomiting, diarrhea) — significantly increases fluid losses

Hydration Sources Beyond Plain Water

Approximately 20% of daily fluid intake comes from food. Water-rich foods like fruits and vegetables make a meaningful contribution. Beverages like herbal tea, milk, and even coffee (in moderate amounts) count toward hydration. Alcohol and very high caffeine intake can increase fluid losses.

Signs of Dehydration

Dark yellow or amber-colored urine
Fatigue, brain fog, or difficulty concentrating
Headaches, especially in the afternoon
Dry mouth, lips, or skin
Decreased urine output (less than 4 times/day)

This tool provides general estimates. Individual needs vary. Consult a healthcare provider for medical concerns about hydration.