How the water intake calculator works
This calculator uses the common guideline of 35 ml of water per kilogram of body weight, adjusted for activity level. Sedentary adults need the base amount; active people and athletes lose more fluid through sweat and need 15–30% more.
Climate, illness, pregnancy, and diet (e.g. high-sodium foods) also affect hydration needs. This is a general estimate — not medical advice.
Why use our water intake calculator?
LaCalc’s water intake calculator is free, fast, and private. No sign-up, no downloads — type your numbers and get instant results. Every calculation runs in your browser, so your data never leaves your device.