About this calculator
This calculator estimates a daily water intake target based on body weight and activity level. It uses the common guideline of 30–35 ml per kilogram of body weight as a baseline, plus an additional allowance for physical activity that generates sweat loss.
A 70 kg adult in the baseline scenario would target roughly 2.1–2.5 L per day. Add another 500 ml–1 L per hour of moderate to vigorous exercise, and additional intake in hot South African summers where sweat losses are higher. All fluids count towards hydration — despite the diuretic myth, coffee and tea contribute to daily fluid intake, though plain water remains the ideal.
The best real-time indicator of hydration is urine colour: pale straw yellow suggests you're well hydrated, dark yellow suggests you should drink more. Rely on thirst as your primary trigger — the human body's thirst mechanism is generally reliable in healthy adults. Very rarely, over-hydration can cause hyponatremia (low blood sodium), so don't force water far beyond thirst and activity needs.
How to use it
- 1Enter your weight. Your body weight in kilograms.
- 2Enter activity minutes. Minutes of moderate to vigorous exercise per day.
- 3Read your daily target. The recommended daily water intake in litres.