Healthy weight range for your height, based on the normal BMI band (18.5–24.9).
We take the Normal BMI band of 18.5–24.9 and solve Weight = BMI × Height(m)² at both ends, giving the minimum and maximum weight considered healthy for your height.
It's the difference between your current weight and the nearer edge of the healthy range — how much you'd need to lose or gain to fall back within the 18.5–24.9 BMI band.
It uses the same BMI formula and thresholds, but inverts the calculation — instead of telling you your BMI from height and weight, it tells you the weight range that corresponds to a healthy BMI for your height.