Daily Water Intake Calculator
Calculate your daily water needs by weight and activity level.
This tool is for informational purposes only. If you have kidney disease or other medical conditions, consult a doctor regarding your daily fluid needs.
Why the '8 Glasses' Rule Doesn't Apply to Everyone
You have probably heard the "everyone should drink 8 glasses of water" rule. The problem is that this rule ignores the difference between 60 kg and 100 kg, activity level, or hot weather. The daily water intake calculator lets you set a personal target based on your weight and lifestyle.
Effect of Exercise and Weather
Significant fluid loss occurs through sweating during exercise. General guideline: 400–600 ml two hours before exercise, 150–250 ml every 15–20 minutes during exercise, and approximately 500 ml per kilogram of weight lost afterwards.
Signs of Dehydration
Dark yellow urine, headache, fatigue and difficulty concentrating are early signs of dehydration. Even a fluid loss of 2% of body weight negatively affects physical and cognitive performance.
Health Benefits of Adequate Hydration
Adequate hydration supports kidney function, lubricates joints, maintains energy levels and improves concentration. Even mild dehydration — just one to two percent of body weight lost — noticeably reduces cognitive performance and physical endurance. The WHO recommends an average daily fluid intake of two to three litres for healthy adults; a portion of this comes from food.
How Do Temperature and Exercise Affect Water Needs?
Fluid losses through sweating are directly proportional to air temperature and exercise intensity. During high heat or intense activity, hourly sweat loss can range from 0.5 to 2 litres. Replacing these losses promptly prevents both dehydration and muscle cramps. Athletes should not neglect regular fluid intake before, during and after exercise.
How to Calculate Daily Water Needs Based on Body Weight?
The most common method of estimating daily water needs is using body weight-based formulas. A common rule is to drink approximately 30-35 ml of water per kilogram of body weight. For a 70 kg adult, the recommended daily water intake is between 2.1 and 2.45 litres. Water consumed from tea, coffee, juice and food can be included in this calculation; however, caffeine and alcohol lower the net fluid balance due to their diuretic effects.