Water Intake Calculator – Daily Hydration Needs
Estimate your daily water intake based on body weight and activity level. Get recommendations in liters, ounces and cups. Stay hydrated for health and performance.
Water Intake Calculator
Estimate daily water needs from weight and activity level.
How the water intake calculator works
Base intake = weight (kg) × 30 ml. Activity multipliers: sedentary 1×, light 1.1×, moderate 1.2×, active 1.35×, very active 1.5×. Results are estimates; adjust based on thirst, climate and health.
Why hydration matters and how to use this calculator
Water is essential for every cell, organ and function. It regulates temperature, transports nutrients, removes waste and cushions joints. Even mild dehydration can affect mood, concentration and physical performance. Most people do not drink enough; this calculator helps you set a daily target based on your size and how active you are.
The formula starts with a base of about 30 ml per kilogram of body weight. A 70 kg person needs roughly 2.1 liters before activity adjustments. If you sit most of the day, that may be enough. If you exercise regularly or work outdoors, you need more. The calculator applies multipliers so your recommendation scales with activity.
Results are in liters, fluid ounces and cups. One cup is 8 fl oz (about 240 ml). Track your intake throughout the day—morning, with meals, during exercise—to meet your target. Thirst is a late signal; by the time you feel thirsty, you may already be slightly dehydrated. Urine color is a useful check: pale yellow usually means good hydration; dark yellow suggests you need more.
Climate, altitude, illness and pregnancy can increase needs. The calculator does not account for these; use it as a starting point and adjust based on your body’s signals. Pair it with our calorie calculator and protein intake calculator for a fuller picture of your nutrition.