You've probably heard "drink 8 glasses a day" â but is that actually right for you? Your optimal daily water intake depends on your body weight, activity level, climate, and overall health. There's no universal answer, but there is a formula.
Find your daily water target based on your weight and activity.
Calculate Water Intake âBaseline: 35ml per kg of bodyweight, adjusted for activity
Base: 70 Ă 35 = 2,450ml
With activity multiplier (Ă1.3): 2,450 Ă 1.3 = 3,185ml (about 13 glasses)
| Activity Level | Multiplier | Example |
|---|---|---|
| Sedentary | Ă1.0 | Office work, minimal exercise |
| Moderate | Ă1.3 | Exercise 3-4 times/week |
| High | Ă1.6 | Daily exercise or physical job |
Yes â despite the mild diuretic effect of caffeine, coffee and tea still contribute net fluid to your intake. The fluid in the drink outweighs the fluid lost through mild diuresis. However, water remains the best hydration source.
Yes â though rare. Hyponatremia (water intoxication) occurs when you drink so much water that your blood sodium becomes dangerously diluted. This mainly affects endurance athletes who drink excessive plain water during prolonged exercise without replacing electrolytes.
The "8Ă8" rule (8 glasses of 8oz = about 2 litres) is a reasonable starting point for an average sedentary adult, but it doesn't account for body size or activity. Our calculator gives a more personalised estimate.
Yes â hot weather and humidity increase water loss through sweat significantly. Add at least 500mlâ1L on hot days or when sweating heavily.
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