Maps BMI to underweight, normal, overweight, and obesity class I–III cut points used in many adult public health dashboards.

Predicts average fatness for demographic groups; systematically mis-estimates highly muscled or depleted patients—pair with clinical judgment.

When you enter a lab- or device-reported %, the page highlights large deltas versus the regression to discuss method disagreement and timing.

Fat mass = weight × body fat%; lean mass is the remainder for classroom intuition—real multicompartment models separate water, bone, and visceral depots.

Flags scenarios where BMI looks “normal” but estimated adiposity is higher—useful for discussing waist measures, triglycerides, and resistance training—not for labeling individuals without data.

Explains why powerlifters and rugby forwards can sit in overweight BMI bands while direct body fat methods read lower—regression was not trained for extreme lean mass.