Weight, age and physical activity has a HUGE factor on the amount of water a person should drink. We know that due to thermo-regulation and our bodies' organs, we lose a lot of water every day. If you exercise a lot, you lose a lot of water via cells that require the water and sweating. According to the U.S. National Academies of Sciences, Engineering, and Medicine, adult males must drink 3.7 litres of water a day and women must drink 2.7 litres. But that is just an estimate since weight and physical activity play a big role too. To conclude, the amount of recommended water to drink daily relies on three factors. Weight, age and physical activity. That is what determines how much water should be drunk daily.
