Kaloretta

How Much Water Should You Drink a Day?

Enter your weight and activity level to see your daily fluid needs in liters and glasses. Remember that everything you drink — and much of what you eat — counts.

Body weight
Activity

All fluids count: water, tea, coffee, soups, vegetables and fruits also provide water. You don't need to drink the target as plain water all at once — spread it throughout the day.

Your daily fluid target

2.8liters

This is about 11 glasses of 250 ml — 33 ml per kilogram of weight plus a bonus for activity.

Base requirement
2.5 L
Activity bonus
+0.3 L

Thirst is a delayed signal: it's better to drink a glass every hour or hour and a half. Discuss the norm with your doctor if you have kidney or heart disease.

How the calculator works

The base is 30 ml of fluid per kilogram of body weight for a mostly sedentary day, rising to 40 ml per kilogram when you are very active. On top of that, the calculator adds a fixed amount for training to cover what you lose through sweat.

Needs also go up in hot weather, at altitude, during illness with fever, and while breastfeeding. On those days drink a little more and let thirst guide you.

What counts towards your daily water

  • Plain and sparkling water, tea, coffee, milk and soups.
  • Water in food: fruit and vegetables provide roughly a fifth of daily fluid for most people.
  • Sugary drinks and juice count as fluid too, but they add calories — keep them small if you are watching your weight.
  • Alcohol doesn’t hydrate: it increases fluid loss, so don’t count it.

Simple habits that help

  • Keep a bottle on your desk or in your bag — you drink more when water is within reach.
  • Start the day with a glass of water and have one with every meal.
  • Check the color of your urine: pale yellow means you are well hydrated.

The result is a guide for healthy adults. With heart or kidney disease, your doctor may set a different fluid limit — follow their advice.

FAQ

How much water should I drink a day?

A practical guide for healthy adults is 30–40 ml per kg of body weight: at 70 kg that is 2.1–2.8 liters. Where you land in that range depends on activity — add 400–600 ml for every hour of exercise. The calculator does this for you.

Do tea and coffee count?

Yes. Your total includes all fluids: tea, coffee, soups, milk, fruit and vegetables (cucumber and watermelon are up to 90% water). Sugary drinks also hydrate you, but they add calories, so plain water is the better default.

Is the "8 glasses a day" rule true?

It is a rough rule of thumb that ignores body size and activity. Eight glasses is about 2 liters: a lot for a 55 kg person at a desk job, too little for 100 kg on training days. Calculating from your weight is more accurate.

Is it OK to drink water with meals?

Yes. Water doesn’t dilute stomach acid enough to affect digestion in healthy people. A glass of water 20–30 minutes before a meal may even take the edge off your appetite, which helps when you are cutting calories.

Can you drink too much water?

Yes: drinking 4–5 liters or more in a short time without salt can cause hyponatremia, a dangerous drop in blood sodium. It is rare, but there is no need to drink "extra just in case" — thirst and pale yellow urine are good everyday signals.