Water Intake Calculator

Estimate how much water to drink each day based on your weight, exercise and climate.

Water to drink per day
98

This is a general estimate of fluids to drink; food provides roughly another 20% of your water. Not medical advice — people with heart or kidney conditions may need to limit fluids.

Where your water need comes from
Baseline: 0.003 (87.6%)Exercise: 0 (12.4%)12.38-oz glasses
  • Baseline0.00387.6%
  • Exercise012.4%
8-oz glasses
12.3 glasses
Baseline (before exercise and heat)
86
Show the working
  1. Baseline: 35 mL × 72.6 kg = 2540 mL
  2. Exercise: 30 min × 12 mL/min = 360 mL
  3. Climate + pregnancy/breastfeeding: 0 mL
  4. Total ≈ 2.90 L

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Formula

Baseline (mL) = 35 × body weight (kg)+ about 12 mL per minute of exercise (≈ 350 mL per 30 min)+ 500 – 1,000 mL in hot weather, + 300 mL pregnant, + 700 mL breastfeeding

How it works

There is no single amount of water that is right for everyone. Needs scale with body size and rise sharply with sweating, which is why this estimate starts from body weight and then adds allowances for exercise, hot weather, pregnancy and breastfeeding.

The baseline of about 35 mL per kilogram is a widely used rule of thumb in clinical nutrition. U.S. reference intakes for total water (drinks plus food) are about 3.7 L a day for men and 2.7 L for women; because food supplies roughly a fifth of that, the drinking-water figure here is usually a bit lower.

All drinks count toward hydration, including tea, coffee and milk. A practical check is urine color: pale straw usually means you are well hydrated. Drinking far more than you need in a short time can be dangerous, especially during long endurance events.

Frequently asked questions

Do I really need eight glasses a day?

"Eight glasses" is a memorable approximation, not a scientific rule. Smaller, less active people may need less; larger or very active people in warm weather may need much more.

Does coffee dehydrate you?

Caffeine has a mild diuretic effect, but in regular coffee drinkers the fluid in the cup more than makes up for it, so it still counts toward your daily intake.

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