Hydration Calculator

Calculate your personalized daily water intake with evidence-based formulas

What is a Hydration Calculator?

A hydration calculator estimates your daily water needs based on your body weight and activity level, using guidelines from the Institute of Medicine and the American College of Sports Medicine. Proper hydration supports all aspects of health, including energy, metabolism, and cognitive function.

Our calculator uses the most trusted formula: Weight × 30 ml (kg) or Weight × 0.5 oz (lbs), plus extra for exercise. This is based on the Institute of Medicine (2005) and ACSM recommendations.

Weight

Your body mass

Activity

Exercise duration

Hydration

Daily water intake

Personal Information

Age (years)

Enter your age in years

Weight (kg)

Enter your weight in kilograms

Height (cm)

Enter your height in centimeters

Height (ft/in)

Enter your height in feet and inches

Gender

Gender affects metabolic calculations

Activity Level

Choose your typical weekly activity level

Climate

Select the climate you live or work in most of the time

Recommended Water Intake

ml/day

Your personalized daily water intake based on weight and activity

Hydration Tips

Hydration Science & Formulas

Water Intake Formula (Transparent)

Mifflin-St Jeor + IOM/EFSA/ACSM:

                  BMR (kcal/day):
                  Men: (10 × weight [kg]) + (6.25 × height [cm]) − (5 × age [y]) + 5
                  Women: (10 × weight [kg]) + (6.25 × height [cm]) − (5 × age [y]) − 161
                  TDEE: BMR × Activity Multiplier × Climate Multiplier
                  Water Intake: TDEE × 1.0 ml/kcal
                

Based on Institute of Medicine (2005), EFSA, and ACSM. This method is used in clinical and research settings for personalized hydration.

Institute of Medicine EFSA ACSM

IOM/EFSA Adequate Intake Table

Reference: IOM/EFSA Population Adequate Intake (AI):

                  Children 1–3 y: 1300 ml/day
                  Children 4–8 y: 1700 ml/day
                  Boys 9–13 y: 2400 ml/day
                  Girls 9–13 y: 2100 ml/day
                  Boys 14+ & Men: 3300–3700 ml/day
                  Girls 14+ & Women: 2300–2700 ml/day
                

These are general population guidelines. Personalized calculation above is more accurate for adults.

Institute of Medicine EFSA

Scientific References

Institute of Medicine (2005)

Establishes evidence-based water intake recommendations for adults.

National Academies Press

EFSA (2010)

European Food Safety Authority: Scientific Opinion on Dietary Reference Values for water.

EFSA Journal

American College of Sports Medicine

Hydration and physical activity consensus statements.

ACSM Position Statements