Water Intake Calculator
Work out how much water to drink each day based on your bodyweight, exercise, climate and more — in litres, glasses and bottles, with NHS guidance.
Not medical advice. This water intake calculator is for general information only and is not medical advice. Speak to your GP about your fluid needs, especially if you have a kidney, heart or other medical condition. Source: NHS Eatwell Guide.
Enter your bodyweight
Your daily water target in litres, glasses and bottles appears here as you type.
How your water target is calculated
We use 35ml per kilogram of bodyweight a day as a baseline, within the commonly cited 30-40ml/kg range for healthy adults. For every 30 minutes of exercise, we add roughly 350ml to replace fluid lost through sweat. A hot climate, pregnancy or breastfeeding, and caffeine or alcohol units each add a further top-up, based on NHS and EFSA guidance. This is a general estimate — actual needs vary with health conditions too, so treat it as a guide and adjust to thirst.