How Much Water Should You Drink Per Day?
Calculate your optimal daily hydration based on body weight, activity level, and climate — beyond the outdated 8-glasses rule.
The 8 Glasses Rule Is Outdated
The "8×8" rule (64 oz/day) has no scientific basis. Actual needs vary by body size, activity, climate, and diet. The National Academies recommend 3.7 L/day for men and 2.7 L/day for women — including water from food (~20% of total).
A Better Formula
Baseline: 0.5 oz per pound of body weight (30–35 ml/kg). Add:
- +12–16 oz per hour of moderate exercise
- +16–24 oz per hour in hot/humid conditions
Example: 180 lb person at rest = 90 oz. With 1 hour of summer exercise = ~110 oz/day.
How to Know You're Hydrated
Use urine color as your monitor — target pale yellow. Dark amber = drink more. Clear = likely overdrinking (rare issue). Thirst is a reliable indicator in healthy adults.
Does Coffee Count?
Yes. Despite mild diuretic effects, coffee and tea contribute to net hydration. Alcohol is a significant diuretic and doesn't count.