Weight, training and heat in one calculation

Water intake calculator

How many liters of water to drink per day, based on your weight, training time and heat. Each part of the math is explained below, with its source.

Water to drink per day
– L
About – 250 ml glasses
Base from body weight – L
Training, heat and life stage – L

Over 16 waking hours, that is one glass every – minutes.

Calculate your daily protein → Water reminders in the app →

Where each part of the math comes from

Values for healthy adults. Food also provides water, about 20% of the daily total.

PartAmountSource
Base from body weight35 ml per kgRule of thumb of 30 to 35 ml/kg used in clinical nutrition
Workout0.5 L per hourSweat of 0.3 to 2.4 L per hour (ACSM, Sawka et al., 2007)
Heat0.5 LSweat rises with temperature and humidity (ACSM, 2007)
Pregnant0.3 LEFSA (2010)
Breastfeeding0.7 LEFSA (2010)
Total reference, including food2.0 L (women) and 2.5 L (men)EFSA (2010)

How to use your result

Spread it over the day

Sipping through the day works better than two liters at once at night. A glass every one or two hours covers most of it.

Check your urine color

Pale yellow means you are well hydrated. Dark means you drank too little. Clear all day long can mean too much water.

Measure your sweat

Weigh yourself before and after training. Each kilogram lost is about one liter of sweat, and you replace it with 1.25 to 1.5 liters per kilogram.

Who needs guidance

Kidney or heart disease and some medications change the amount, sometimes downward. In those cases, your doctor decides.

Frequently asked questions

How many liters of water should I drink per day?
A rule of thumb dietitians use is 30 to 35 ml per kg of body weight: about 2.6 liters for someone who weighs 75 kg. The European Food Safety Authority (EFSA, 2010) reference is 2.0 liters of total water per day for women and 2.5 liters for men, counting drinks and food.
How much extra water on training days?
On average 0.4 to 0.8 liters per hour of training, but sweat loss ranges from 0.3 to more than 2 liters per hour depending on the person, the intensity and the heat (ACSM position stand, Sawka et al., 2007). This calculator adds 0.5 liters per hour of training.
How do I know how much I sweat?
Weigh yourself before and after a workout, without sweaty clothes. Each kilogram lost is about one liter of sweat. To replace it, the ACSM suggests drinking 1.25 to 1.5 liters per kilogram lost, gradually, over the next few hours.
Does food count as water?
It does. Fruit, vegetables, soups and dairy provide about 20% of daily water, according to EFSA. If you eat plenty of fruit and vegetables you can drink a little less than the result, and thirst adjusts the rest.
Can drinking too much water be harmful?
It can. Drinking much more than you lose, in a short time, dilutes the sodium in your blood (hyponatremia). The risk is highest in long events, when people drink nonstop and gain weight during the race. Day to day, follow your thirst and the color of your urine, which should be pale yellow.

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Personal trainer? Your clients remember to drink water

In the Trainer Connect app, clients log each glass on the Hydration card and can turn on a reminder every 2 hours that stops by itself once they hit the daily goal. You handle training and nutrition in the same place.

Start for free

Estimate for healthy adults. It does not replace advice from a doctor or dietitian, especially with kidney or heart disease, diuretics, pregnancy or endurance events.