Water Intake Calculator
Enter the requested values and units to calculate the numeric result using the stated formula.
Breakdown
Calculation only
The output is produced only from the values, units, and formula shown by this tool.
This tool does not compare the number with a clinical range, assign a category, diagnose a condition, or recommend an action. Check that your input units match the form and use your laboratory report or a qualified medical professional for interpretation.
How the calculation works
The tool multiplies body weight by 32.5 ml per kilogram and adds a fixed volume for the selected activity level and for the selected climate. The multiplier and the additions are constants in the code, not a published equation.
Formula
- Base volume (ml) = weight (kg) × 32.5
- Activity addition (ml), by selected option: sedentary 0, lightly active 350, moderately active 500, very active 750, extremely active 1000
- Climate addition (ml), by selected option: temperate 0, hot / humid 500, cold 250, altitude 500
- Total (ml) = base volume + activity addition + climate addition
- Glasses = total (ml) ÷ 250, rounded to a whole number
- Volume per hour = total (ml) ÷ 16
Units
Weight in pounds is divided by 2.20462 to obtain kilograms. Metric mode shows liters (ml ÷ 1000) with one decimal and the hourly value in ml; imperial mode shows US fluid ounces (ml ÷ 29.5735) as whole numbers.
Limits of the calculation
- The 32.5 ml per kilogram multiplier, the activity and climate additions, the 250 ml glass and the divisor of 16 hours are fixed constants in the code; no publication is cited for them.
- The calculation uses only body weight and the two selections; it has no term for age, sex, height or diet.
- The code rejects an empty, zero or negative weight and applies no upper bound.
- Liters are shown with one decimal and ounces as whole numbers; switching the unit toggle converts the entered weight and rounds it to one decimal.