How the water intake calculator works
Your target has three parts:
- Base needs: about 33 ml per kilogram of body weight. A 70 kg person starts at roughly 2.3 litres.
- Exercise: about 350 ml for every 30 minutes of training, to replace sweat losses.
- Climate: an extra 0.5 litres in hot or humid weather.
Add them up and you get a daily fluid target in litres and 250 ml glasses. These are common rules of thumb, not lab measurements, so use them as a starting point.
How this compares with official guidance
Health bodies give general figures for total water from food and drink. The European Food Safety Authority, for example, suggests about 2.0 litres a day for women and 2.5 litres for men. Since food provides some of that, a personalised drinks target like this one is a practical everyday guide.
Easy ways to hit your target
- Start the day with a glass before tea or coffee.
- Keep a 1-litre bottle at your desk and aim to refill it two or three times.
- Drink with every meal. It also helps you eat more slowly.
- Pre-load before training: about 400–600 ml in the two hours before a workout.
- Use your urine colour: aim for pale yellow.
Hydration and fat loss
Water doesn’t burn fat by itself, but it helps. Thirst is easily mistaken for hunger, and starting meals with a glass of water can help you eat a little less. Good hydration also keeps training performance up, which matters when you’re in a calorie deficit.
Limitations
People with heart, kidney or liver conditions, or those told to limit fluids, should follow their doctor’s advice. Athletes training for hours in heat need individual hydration and electrolyte plans.
