Fitness estimates

General fitness estimates — not medical advice: body mass index from height and weight, healthy weight range from standard BMI cutoffs, training heart-rate zones from age and resting pulse, and daily water intake guidelines. Useful for screening and workout planning; talk to a clinician before changing diet, hydration, or exercise based on these numbers alone.

It helps to know what each number can and cannot tell you. BMI is a ratio of weight to height squared; it was designed to describe populations, not individuals, and it cannot distinguish muscle from fat, which is why well-trained athletes frequently land in the overweight band while carrying little body fat. Age-based heart-rate zone formulas carry a wide margin of error across individuals, so treat the boundaries as approximate and use perceived effort alongside them. Hydration guidelines shift with climate, body size, activity, and medication. These are screening and planning aids: a result outside a typical range is a reason to ask a clinician a question, not a diagnosis on its own.