Water Intake Calculator

Calculate how much water you should drink daily based on your weight, activity level, and climate.

This calculator starts from the classic baseline of half an ounce of water per pound of body weight per day — 85 ounces for a 170 lb person — then layers on fixed additions rather than percentages. Activity adds 16 ounces for moderate exercise, 32 for daily training, and 48 for intense work; climate adds 16 for hot and humid conditions or 24 for very hot ones. Because those adjustments are flat ounces, Activity Level is the biggest lever for most people: switching from sedentary to very active adds 48 ounces, which equals the entire baseline contribution of 96 pounds of body weight. The flip side of flat additions is that their importance shrinks as you get heavier — the same 16-ounce hot-climate bump is a 19 percent increase at 170 lbs but under 10 percent at 350 lbs. Everything else on the results panel is unit conversion of the same total: cups divide by 8, liters multiply by about 0.0296, and the glass and bottle counts round UP, so you will always see a whole extra glass rather than a fractional one. What the model leaves out: food moisture (typically a fifth of intake), caffeine and alcohol effects, altitude, pregnancy, and kidney or heart conditions that change fluid targets.