Santé & Physiologie • Recommandations EFSA / OMS

Daily Water Intake & Hydration Calculator

Q: Where does the '8 glasses or 2 liters a day' rule originate from?

The European Food Safety Authority (EFSA) suggests 2.0 L for women and 2.5 L for men under moderate climate and rest. However, this is an average baseline: heavier individuals or athletes require proportionally higher fluid intake.

Q: Do tea and coffee count toward daily hydration totals?

Yes, herbal infusions, tea, and moderate coffee contribute positively to your hydration. While caffeine has mild diuretic properties in large doses, the net fluid gain remains positive.

Q: Can drinking too much water be dangerous (water intoxication)?

Consuming excessive volumes (over 5-6 liters in a few hours) without electrolytes can cause hyponatremia, dangerously diluting blood sodium levels. Always pace fluid intake steadily.

Q: How should athletes hydrate during workout sessions?

Drink 200-300 mL half an hour prior to working out, then take 100-150 mL sips every 15-20 minutes. Weigh yourself before and after: each kilogram lost equals 1 liter of fluid to recover.

Accurately estimate your optimal daily water volume based on body weight, workout intensity, and ambient climate conditions.

Body Profile & Lifestyle Factors

Biological sex

Age group

Body weight (kg)70 kg

30 kg70 kg110 kg150 kg

Daily physical activity

Climate & Ambient Temperature

Your Recommended Water Volume

Liters of water per day

2.8Litres / jour

Daily target hydration level62%

Glasses of 250 mL (8 oz)

11verres

500 mL water bottles

5.6gourdes

Optimal Daily Hydration Schedule

1. Upon waking (empty stomach) : ~500 mL1 to 2 glasses (300 - 500 mL) to kickstart your metabolism and rehydrate organs after sleep.

2. Around main meals : ~800 mL1 glass (250 mL) 30 min before meals. Avoid heavy drinking during eating to preserve gastric enzyme concentration.

3. During & after exercise : ~600 mLSip small quantities every 15-20 minutes of physical effort, and replenish sweat losses afterwards.

4. Afternoon & Evening : ~900 mLMaintain steady fluid intake throughout the day. Ease off 1 hour before bed to support uninterrupted restful sleep.

How much water should you drink daily based on weight and activity?

Water constitutes roughly 60% of an adult's body weight. Each day, our body naturally expels 2 to 2.5 liters through perspiration, respiration, and urination. Replenishing these fluids is critical to mental sharpness, joint health, and energy levels.

Dehydration indicators and food fluid contributions

Feeling thirsty signals that you have already lost 1% to 2% of your body water weight, causing up to a 10% dip in cognitive focus and physical stamina. Dark urine and headaches are primary symptoms. Tip: Approximately 20% of your daily fluids come from solid food moisture (cucumbers, watermelon, berries), while the remaining 80% must come from direct beverages.

Daily Water Intake Reference by Body Weight and Routine

Body Weight	Sedentary (< 20°C)	Moderate Exercise	Intense Sport / Hot Climate	Glasses (250 ml / 8 oz)
50 kg (Enfant / Petit gabarit)	1,8 L	2,1 L	2,8 L	7 à 11 verres
60 kg	2,1 L	2,5 L	3,2 L	8 à 13 verres
70 kg (Moyenne adulte)	2,5 L	2,9 L	3,6 L	10 à 14 verres
80 kg	2,8 L	3,2 L	4,0 L	11 à 16 verres
90 kg	3,2 L	3,6 L	4,4 L	13 à 18 verres
100 kg et plus	3,5 L	3,9 L	4,8 L	14 à 19 verres

Frequently Asked Questions about Daily Water Intake

Where does the '8 glasses or 2 liters a day' rule originate from?

The European Food Safety Authority (EFSA) suggests 2.0 L for women and 2.5 L for men under moderate climate and rest. However, this is an average baseline: heavier individuals or athletes require proportionally higher fluid intake.

Do tea and coffee count toward daily hydration totals?

Yes, herbal infusions, tea, and moderate coffee contribute positively to your hydration. While caffeine has mild diuretic properties in large doses, the net fluid gain remains positive.

Can drinking too much water be dangerous (water intoxication)?

Consuming excessive volumes (over 5-6 liters in a few hours) without electrolytes can cause hyponatremia, dangerously diluting blood sodium levels. Always pace fluid intake steadily.

How should athletes hydrate during workout sessions?

Drink 200-300 mL half an hour prior to working out, then take 100-150 mL sips every 15-20 minutes. Weigh yourself before and after: each kilogram lost equals 1 liter of fluid to recover.

About the Daily Water Intake Calculator & Hydration Guide

Accurately calculate your optimal daily water intake to maintain peak energy, concentration, and athletic performance. Grounded in EFSA and WHO hydration guidelines, our tool factors in body weight (30-35 mL per kg), biological sex, age bracket, daily workout intensity, climate temperature, and pregnancy or lactation status. Track your equivalent in 250 mL glasses and 750 mL sports bottles, and follow a practical hourly drinking schedule from morning to night.

Smart Assistant & Intelligent Analysis

Automated calculation optimization & decision support

Automated optimization: Predictive target heart rate zone calibration (advanced Karvonen formula based on heart rate reserve), personalized cardiovascular strain analysis, and metabolic modeling tailored to your body composition.