WATER INTAKE
CALCULATOR
Find your exact daily water target based on weight, activity level, and climate.
What This Calculator Does
The Water Intake Calculator gives your personalised daily hydration target based on body weight, activity level, and climate. It uses the National Academies of Sciences 30–35ml per kg guideline plus exercise adjustment.
The Formula Explained
Base: 30–35ml per kg body weight. Add 500ml per 30 minutes of exercise. Hot climate: add 10–20%. Example: 75kg, moderately active → 75 × 33ml = 2,475ml base + 500ml exercise = ~3L daily target.
What Your Result Means
Even mild dehydration (1–2% body weight) reduces cognitive performance by up to 20% and impairs exercise output. The '8 glasses' rule is not evidence-based — individual needs vary by 2–3× based on size, activity, and climate. Urine colour is the best real-time indicator: aim for pale yellow.
Calorie Calculator for complete nutrition planning · Read: How Much Water Should You Drink?
How Much Water Do You Need?
The widely cited 'eight glasses a day' rule is not based on scientific evidence. Optimal hydration depends on body weight, activity level, climate, and individual physiology. The most evidence-backed approach uses body weight as the baseline: approximately 0.5 fluid ounces per pound of body weight per day (or 30–35ml per kg), adjusted for activity and environment.