Water intake calculator

Estimate how much water you should drink daily based on your weight, activity level, and environment.

Water intake calculator inputs

kg
Daily water intake
2.8 litres
Glasses (250 ml)
11 glasses
Bottles (500 ml)
5.6 bottles
Per hour (waking)
175 ml

How is daily water intake calculated?

The baseline recommendation is approximately 35 ml per kg of body weight. This is then adjusted upward for activity level and climate:

Water (litres) = weight (kg) × 0.035 + activity adjustment + climate adjustment

The adjustments account for fluid lost through sweat during exercise and in hot environments.

Signs of dehydration

  • Dark yellow urine — pale straw colour indicates good hydration
  • Thirst — by the time you feel thirsty, you may already be mildly dehydrated
  • Headaches and fatigue — common early symptoms
  • Dry mouth and lips
  • Decreased urination — fewer than 4 times a day may indicate dehydration

Tips for staying hydrated

  • Start your day with a glass of water before tea or coffee.
  • Keep a water bottle at your desk and refill it regularly.
  • Drink a glass of water before each meal.
  • Set reminders if you tend to forget — every 1-2 hours.
  • Eat water-rich foods: cucumber, watermelon, oranges, yogurt.

Frequently asked questions

Can I drink too much water?

Yes, though it's rare. Overhydration (hyponatremia) occurs when you drink so much water that sodium levels in your blood drop dangerously. This is most common during endurance sports. For most people, drinking to thirst is a safe guide.

Does the "8 glasses a day" rule hold up?

The "8×8" rule (eight 8-oz glasses ≈ 1.9 litres) is a reasonable minimum for a sedentary person in a temperate climate, but it doesn't account for body weight, exercise, or heat. A personalised calculation is more accurate.

Should I drink more water while pregnant or breastfeeding?

Yes. Pregnant women should add about 0.3 litres/day to their baseline, and breastfeeding women should add about 0.7-1.0 litres/day to support milk production.

Related calculators