How it is calculated

Multiply your weight by the Vietnam Ministry of Health ml/kg rate for your age: 40 ml/kg under 19 (and 19–30 with high activity), 35 ml/kg from 19 to 54, 30 ml/kg from 55.
Never go below the EFSA adequate total water intake: 2.0 litres for women, 2.5 litres for men.
Multiply by 0.8, because food supplies about 20% of your water, and keep it between 1.5 and 3.2 litres.
Add 250 ml for moderate activity, 500 ml for high activity, 250 ml when pregnant, 700 ml when breastfeeding and 500 ml for outdoor work. With a history of kidney stones, aim for at least 2.5 litres.
Children under 14 use the EFSA reference for their age (1.6 litres under 9; 1.9–2.1 litres from 9 to 13) × 0.8.

Examples

Woman, 30, 50 kg, low activity: 50 × 35 = 1,750 ml, below the EFSA 2,000 ml, so 2,000 × 0.8 = 1,600 ml a day.
Man, 25, 80 kg, high activity: 80 × 40 = 3,200 ml × 0.8 = 2,560 ml, plus 500 ml ≈ 3,050 ml a day.

If you have a heart, kidney or liver condition, or your doctor has limited your fluids, follow your doctor’s advice instead of this number.

ThirstyBot does not replace medical advice. If you have a medical condition, ask your doctor how much water is right for you.