How Much Water to Drink a Day by Weight (Chart)

Mealyno multiplies body weight by an activity factor: 30 ml per kg if you are sedentary, 31 if lightly active, 33 if moderately active, 34 if active and 35 if very active. Hot weather adds 500 ml. The result is rounded to 50 ml and kept between 1.5 and 4.0 litres. It is a general guide, not a medical recommendation, and it counts drinks only.

Litres a day for a healthy adult in mild weather. The last column shows the same weight with hot weather and a very active day.

For a 70 kg moderately active adult the goal is 2.30 litres, about 9 cups of 250 ml or 4.5 bottles of 500 ml. Spread over 16 waking hours that is roughly 140 ml an hour, which is easier to follow than one number at the end of the day. Tea, coffee, milk and water-rich food all contribute, and sugary drinks are better treated as a separate line.

One way to spread 2.30 litres is four blocks across the waking day: about 700 ml from waking to late morning, 700 ml through the afternoon, 600 ml in the evening and the rest around meals. The split is only an example to make the number easier to use, not a rule. If you wake at night thirsty or finish a long workout, adjust it and drink to thirst.

The European Food Safety Authority sets an adequate intake of total water, drinks plus the water in food, of 2.0 litres a day for adult women and 2.5 for adult men. About 20 % of that usually comes from food, which leaves around 1.6 litres of drinks for women and 2.0 for men. The weight-based chart gives lower or higher numbers depending on size and activity, and both approaches describe adequate intakes for healthy adults, not requirements for one person.

Children and teenagers have their own reference values, so the chart is for adults only, and Mealyno's calculator declines under 18. If you are pregnant or breastfeeding, have a kidney, heart or liver condition, or have been told to limit fluids, follow your doctor's number, not this one. Large changes in thirst or very dark urine are worth mentioning to a doctor. Drinking far more than you need is not a goal. Illness with fever, vomiting or diarrhoea, long periods in the heat and heavy sweating at work or in sport all change how much you lose, so treat the chart as a baseline for an ordinary day and ask a doctor if you are unsure.

The hydration tracker in the app uses the same goal. You log what you drink, and the goal adjusts for your weight, activity and hot days, and adds 300 ml in GLP-1 mode. You can also set your own number if your doctor gave you one. Every adult in a household has their own goal because the chart depends on weight, so two adults at the same table rarely share one number.