What is it?
Water needs vary with body size, activity, climate and diet. Most healthy people can use thirst as a guide, but a target helps if you train hard or often forget to drink.
How it's calculated
Base: 35 ml per kg of body weight.
Exercise: +350 ml per 30 minutes.
Hot or humid climate: +500 ml.
Result is bounded between 1.5 and 5 litres per day.
How we calculate · Last reviewed: September 1, 2026
How to interpret your result
Pale-yellow urine is a simple sign of good hydration.
People with heart or kidney conditions may need fluid limits — follow medical advice.
Estimates for healthy adults. Not medical advice — talk to a qualified professional about your specific situation.