I agree with this calculation for sure but I add extra water on days where im working harder and sweating more. I good way to tell is if your pees too dark yellow you need water and if its clear you need sodium or electrolytes. Im 195lb and drink about 4L a day in the summer maybe 3ish in winter. I add 2/3 to 3/4 teaspoon of Himalayan pink salt to my 4l jug and have sometimes added 1 to 2 teaspoons of natural pure maple syrup as glucose is needed for your body to absorb the electrolytes.