The base formula is 33 ml per kg of body weight, with an additional 350 ml for every 30 minutes of daily exercise. This reflects current European Food Safety Authority and WHO guidance.

Mostly yes. At moderate doses (up to 400 mg caffeine/day), the mild diuretic effect of caffeine is offset by the water in the beverage. Plain water remains the best source, but coffee and tea do contribute.

Yes. Add at least 500 ml per hour of sweating activity in heat. At high altitude (above 2,500 m), increased respiration rate raises fluid loss — add 500–1,000 ml/day until acclimatised.

Pale yellow urine (straw-coloured) indicates good hydration. Dark yellow or amber signals dehydration. Clear urine may indicate over-hydration. Aim for pale yellow throughout the day.