Hydration Calculator Formula
Understand the math behind the hydration calculator. Each variable explained with a worked example.
Formulas Used
Daily Water (liters)
daily_liters = base_liters * activity_levelDaily Water (ounces)
daily_oz = base_liters * activity_level * 33.814Daily Water (cups)
daily_cups = base_liters * activity_level * 33.814 / 8Variables
| Variable | Description | Default |
|---|---|---|
weight_lbs | Body Weight(lbs) | 170 |
activity_level | Activity Level | 1 |
weight_kg | Derived value= weight_lbs * 0.453592 | calculated |
base_liters | Derived value= weight_kg * 0.033 | calculated |
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
- 01Weight in kg = 170 x 0.4536 = 77.1 kg
- 02Base water = 77.1 x 0.033 = 2.54 liters
- 03Adjusted = 2.54 x 1.4 = 3.56 liters
- 04In ounces = 3.56 x 33.814 = 120 oz
Frequently Asked Questions
How much water should I drink?
A general rule is 0.033 liters per kg of body weight. Adjust upward for exercise, hot weather, and altitude.
Learn More
Guide
Hydration Guide: How Much Water Do You Really Need?
Learn how to calculate your daily water intake based on weight, activity level, and climate. Understand the signs of dehydration and how to stay properly hydrated.
Ready to run the numbers?
Open Hydration Calculator