Daily Water Intake

Base 0.5 oz/lb (33 mL/kg) + 12 oz per 30 min exercise.

Inputs

Result

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How to use this calculator

  • Weight + unit + activity.
  • Climate adjustment.

About this calculator

Standard rules of thumb: 0.5 oz per lb body weight (33 mL per kg), plus 12 oz per 30 minutes of exercise. Hot or altitude environments: +25%. WHO recommends 2-3 L/day; varies wildly by individual. Indicators: pale yellow urine = adequate; dark = dehydrated. Don't over-drink (hyponatremia risk in long endurance events). Source: National Academies of Sciences (2004 — Dietary Reference Intakes).

Frequently asked

Is "8 cups" a real rule?+
Approximate. Real need varies 1-4 L based on size + activity + climate. Use this calc for personalized estimate.
Can you over-drink?+
Yes — hyponatremia (low sodium). Risk in marathon runners drinking only water. Add electrolytes for >2hr exercise.
Coffee count?+
Yes — recent research: caffeine's diuretic effect is mild. Coffee/tea contributes to hydration.
Other indicators?+
Urine pale yellow = good. Dark amber = drink more. Clear = over-hydrating.
Sources of water?+
Food provides ~20%. Soup, fruits (watermelon), vegetables (cucumber) all count. Total includes beverages + food water.

Related calculators

Daily Protein by Body Weight
Daily protein need = body weight × g/kg target. RDA 0.8 g/kg; athletic 1.6-2.2 g/kg.
Sweat Rate Calculator
Sweat rate (L/hr) = (pre-weight − post-weight + fluid intake) / duration.
Caffeine Half-Life Clearance
Caffeine t½ ≈ 5 hr in adults. Dose × 0.5^(hours/5) = remaining.
Daily Sodium Target
AHA limit: 1500 mg ideal, 2300 mg max. Athletes lose 500-1500 mg/hr in sweat.
Daily Fiber Target
Adults: 25 g women / 38 g men. Most US adults get half that.
Rest Day / Recovery Calculator
Recommended rest days = base + intensity adjustment − sleep credit + age adjustment.

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Daily hydration needs by bodyweight + exercise + climate.