Health & Fitness

Water Intake Calculator

Calculate your personalized daily water intake goal based on weight and activity.

General hydration guidelines are too generic. Your daily water needs depend on body weight, activity level, climate, and diet. This calculator gives you a personalized target in both ounces and liters.

Enter your numbers

Weight (lbs)

Activity Level

Hot Climate or Sweating Heavily?

Results update as you change the inputs. Calculations run in your browser.

Daily Water Goal

99 oz

liters: 2.9 L
glasses: 13 glasses (8 oz each)
baseline: 83 oz baseline without activity

See the formula

Formula and method

Ounces = Weight(lbs) × Activity Multiplier (0.5-0.7)

Based on the general guideline of 0.5 oz per pound of body weight at rest, with multipliers for activity level. Hot climate increases requirement by 10%.

Worked examples

Office worker

Weight (lbs):: 160
Activity Level:: Sedentary (desk job, no exercise)
Hot Climate or Sweating Heavily?:: No

Daily Water Goal: 80 oz

Marathon runner in summer

Weight (lbs):: 155
Activity Level:: Very Active (athlete/physical labor)
Hot Climate or Sweating Heavily?:: Yes

Daily Water Goal: 119 oz

Assumptions and limits

Temperate climate as baseline
No medical conditions affecting fluid regulation

This tool provides an educational estimate. Rules, rates and personal circumstances can change the answer. Review the assumptions before relying on a result. Report a correction.

Common mistakes to avoid

Drinking all water at once — hydration works best distributed throughout the day.
Not counting water from food — fruits and vegetables provide significant hydration.
Only drinking when thirsty — by the time you feel thirsty, you are already mildly dehydrated.

Frequently asked questions

Does coffee count toward water intake?

Moderate coffee consumption (up to 3-4 cups/day) does not cause net dehydration despite its mild diuretic effect. It can partially count toward daily fluid intake, but plain water is best.

Is there such a thing as too much water?

Yes. Hyponatremia (water intoxication) is a rare but real condition, most commonly seen in endurance athletes. For most people, the kidneys can process up to about 1 liter per hour, far above normal drinking patterns.