Should I drink more water during exercise?

Yes. Add approximately 500 ml to 1 litre per hour of moderate exercise, and more for intense or prolonged sessions. In hot and humid weather, especially during summer, increase this further because sweat losses rise sharply. Drink steadily before, during, and after activity rather than waiting until you feel thirsty.

Can I drink too much water?

Yes. Overhydration, called hyponatraemia, can be dangerous because it dilutes the sodium in your blood. This is rare in normal circumstances but can occur if someone drinks several litres of water in a short period without adequate sodium, which is most often seen in endurance athletes. Spread your intake across the day instead of forcing large volumes at once.

Does the water in food count?

Yes. Approximately 20 percent of daily water intake comes from food, particularly fruits and vegetables such as watermelon, cucumber, oranges, and tomatoes, along with soups, yoghurt, and cooked grains. This calculator gives your total fluid target from all sources, so you do not need to drink the entire amount as plain water.

Why does the recommendation change with body weight?

Larger bodies have more cells that require hydration, more blood volume to maintain, and generally higher metabolic rates that produce more waste products requiring water to flush out. That is why the calculation scales with weight instead of giving everyone the same fixed number of glasses.

Should I drink more water during exercise?

Yes. Add approximately 500 ml to 1 litre per hour of moderate exercise, and more for intense or prolonged sessions. In hot and humid weather, especially during summer, increase this further because sweat losses rise sharply. Drink steadily before, during, and after activity rather than waiting until you feel thirsty.

Can I drink too much water?

Yes. Overhydration, called hyponatraemia, can be dangerous because it dilutes the sodium in your blood. This is rare in normal circumstances but can occur if someone drinks several litres of water in a short period without adequate sodium, which is most often seen in endurance athletes. Spread your intake across the day instead of forcing large volumes at once.

Does the water in food count?

Yes. Approximately 20 percent of daily water intake comes from food, particularly fruits and vegetables such as watermelon, cucumber, oranges, and tomatoes, along with soups, yoghurt, and cooked grains. This calculator gives your total fluid target from all sources, so you do not need to drink the entire amount as plain water.

Why does the recommendation change with body weight?

Larger bodies have more cells that require hydration, more blood volume to maintain, and generally higher metabolic rates that produce more waste products requiring water to flush out. That is why the calculation scales with weight instead of giving everyone the same fixed number of glasses.

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Water Intake Calculator

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Daily Hydration

How Much Water Should You Drink Per Day?

The daily water intake recommendation depends on your body weight, activity level, and climate. The commonly cited 8 glasses per day is a useful starting guideline, but your actual needs are more personalised than a single fixed number. Body size, how much you sweat, the temperature around you, and even the food you eat all shift the target up or down.

The standard medical recommendation from institutions including the National Academies of Medicine is approximately 3.7 litres per day for men and 2.7 litres for women from all beverages and food combined. That total includes tea, coffee, milk, soups, and the water naturally present in fruits and vegetables, not just plain drinking water.

Step-by-step

How to use this calculator

1Enter your body weight in kilograms. Use your current weight rather than a target weight for the most accurate baseline.
2Select your activity level so the calculator can account for fluid lost through sweat during exercise or physical work.
3Indicate whether you live in or are currently experiencing a hot climate, which raises your requirement further.
4Read your recommended daily intake in litres and glasses, then split it across the day rather than drinking it all at once.
5Recheck the number if your weight, training routine, or the season changes, since your needs move with them.

Methodology

How This Calculator Works

This calculator uses your body weight as the primary input and applies the widely used formula of 35 millilitres per kilogram of body weight as a baseline. For a 70 kg adult, that produces roughly 2.45 litres per day before any adjustments.

It then adjusts upward for physical activity and hot climate conditions, which increase fluid loss through sweat. Exercise typically adds 500 millilitres to 1 litre per hour of moderate effort, and sustained heat adds a further allowance on top of the baseline.

Warning Signs

Signs You Are Not Drinking Enough Water

Dark yellow or amber coloured urine
Feeling thirsty, since thirst is already a sign of mild dehydration
Headaches and difficulty concentrating
Dry mouth and lips
Fatigue and low energy
Dizziness when standing up quickly

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