11 Smart Scale Metrics Explained: Body Composition, Accuracy, and How to Use Them

7. Body Water Percentage

Body water percentage estimates how much of your weight is water. Hydration strongly affects BIA readings because electrical current flows differently through water and electrolytes. Typical ranges vary by age and sex but fall roughly between 45% and 65% for many adults. Rapid increases or drops in body water can come from salts, carbohydrates, menstrual cycle changes, or recent exercise. For reliable tracking, measure under steady conditions. Drinking a large glass of water before stepping on the scale can temporarily increase your body-water reading and lower apparent body-fat percentage. Some advanced scales try to separate intracellular and extracellular water, but those estimates are even more sensitive to short-term changes. Use water percentage to check hydration trends: a morning routine that includes weighing before breakfast helps you compare like with like. If you’re monitoring hydration for sport or health reasons, pair scale readings with subjective signs—thirst, urine color—and seek medical advice if levels swing dramatically.