Water intake calculator
Calculates daily fluid needs from body weight with adjustments for physical activity and hot climate.
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Calculation
Result
- Total water
- 2500ml/day
- Of that, from drinks
- 1880ml/day
- Equivalent
- 8glasses of 250 ml
- Baseline requirement
- 2250ml/day
- Activity adjustment
- 250ml/day
- Climate adjustment
- 0ml/day
Including water that comes from food
75% of the daily requirement
Unit: ml/day, period: one day. Method source: EFSA Dietary Reference Values for water (2010) and ACSM fluid replacement guidance.
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How it is calculated
The baseline is 30 ml per kg of body weight for adults and 25 ml/kg after 60, when renal concentrating ability declines. Each hour of intense activity adds 500 ml to cover sweat losses, and a hot climate or dry heated room adds another 500 ml. The total is full water requirement; 20–30% of it comes from food, so the amount that must come from drinks is shown separately (EFSA, 2010).
Formula
Total(ml) = weight × 30 (or × 25 after 60) + 500 × hours of activity + 500 in heat; Drinks(ml) = total × 0.75
Limits of the method
A reference point for healthy adults. In heart or kidney failure, on diuretics, during fever and in hot industrial work the target is set by a physician. Thirst and urine colour remain more reliable guides than any formula.
Sources of the method
This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.
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What next
Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.
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