Estimate daily water intake from body weight using a simple milliliters-per-kilogram rule—a common starting point in sports-nutrition handouts and wellness apps before adjusting for climate, activity, or medical conditions.
Formula
Daily intake (ml) = weight (kg) Ă— ml per kg
The default coefficient is 35 ml/kg (often cited as roughly one ounce per pound of body weight). You can change ml per kg to model other guidelines—for example, 30 ml/kg for sedentary adults or 40–45 ml/kg during heavy training. The result is rounded to the nearest whole milliliter.
When to use it
Useful for quick hydration planning, comparing guideline coefficients, teaching the weight-based rule in nutrition courses, or sanity-checking tracker goals before consulting a dietitian.
Limitations
Accepts body weight from 1 to 500 kg and ml per kg from 1 to 100; values outside those ranges return an error. The formula ignores sweat rate, altitude, pregnancy, kidney disease, diuretics, and fluid already consumed from food. It outputs a single daily total, not hourly targets.
Example
A 70 kg person at the default 35 ml/kg yields 2,450 ml (about 2.5 liters) per day.
Health disclaimer
This tool provides educational estimates only—not medical advice. Fluid needs vary with health status, medications, and environment. Consult a qualified healthcare professional before changing diet, hydration, or weight goals, especially if you have heart, kidney, or electrolyte disorders.