Hydration Calculator Formula

Understand the math behind the hydration calculator. Each variable explained with a worked example.

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Formulas Used

Daily Water (liters)

daily_liters = base_liters * activity_level

Daily Water (ounces)

daily_oz = base_liters * activity_level * 33.814

Daily Water (cups)

daily_cups = base_liters * activity_level * 33.814 / 8

Variables

VariableDescriptionDefault
weight_lbsBody Weight(lbs)170
activity_levelActivity Level1
weight_kgDerived value= weight_lbs * 0.453592calculated
base_litersDerived value= weight_kg * 0.033calculated

How It Works

Weight-Based Hydration Formula

Base Water (liters) = Weight (kg) x 0.033

Adjusted Water = Base x Activity Multiplier

This formula is the standard metric approach. Active individuals need 20-60% more water than sedentary ones.

Worked Example

A 170 lb moderately active person.

weight_lbs = 170activity_level = 1.4
  1. 01Weight in kg = 170 x 0.4536 = 77.1 kg
  2. 02Base water = 77.1 x 0.033 = 2.54 liters
  3. 03Adjusted = 2.54 x 1.4 = 3.56 liters
  4. 04In ounces = 3.56 x 33.814 = 120 oz

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