Calculate your daily water intake based on body weight and activity level. Free hydration calculator.
Estimate your daily water intake recommendation based on body weight, activity level, and climate. Results are in liters and cups/oz.
The popular "8×8" rule (eight 8-oz glasses) isn't backed by strong evidence — it's a rough approximation that works for sedentary adults in temperate climates. Your actual needs vary by body size, exercise, heat, and diet (fruits and vegetables contain significant water).
You lose roughly 0.5–1 liter per hour of moderate exercise through sweat. In hot weather or intense exercise, this can be 1–2 liters per hour. Add that to your baseline. Electrolytes matter too — plain water during very long exercise sessions can dilute sodium.
This calculator estimates total daily water intake including beverages. Roughly 20% of water intake typically comes from food. The calculator result is for all fluids combined.
Yes — add roughly 350–500 ml (12–17 oz) of water per 30 minutes of moderate exercise. In hot weather or intense workouts, you may need 500–750 ml extra per hour.
How Much Water Should You Drink Per Day?