Body measures
Adult BMI and waist-to-height ratio, with an optional energy estimate.
About this tool
Calculate or Enter runs the example inputs or your own measurements. Edits remove the previous output; Reset restores the examples. No personal inputs are stored after leaving.
BMI and waist
BMI = kg / metres², using CDC adult categories for age 20+: boundaries 18.5/25/30/35/40. Waist divided by height is a separate screening ratio. It does not classify underweight, overweight or obesity. For BMI below 35, NICE central-adiposity bands are 0.4 to below 0.5, 0.5 to below 0.6 and 0.6 or above. Below 0.4 or at BMI ≥35, this tool shows the ratio without a class. Boundaries use unrounded values. No claim about personal overall health or body-fat percentage.
Measurement
Measure waist midway between the lowest ribs and the top of the hips after breathing out naturally; use a level tape without squeezing. Use the same unit for waist and height. A blank waist omits only that row; an invalid one reports a field error while valid BMI/energy remain available. BMI reference weight is the mathematical interval 18.5 ≤ BMI <25, with rounded display limits, not a personal target.
Optional energy
Enable Estimate energy to enter age, formula reference and a rough activity factor. Simplified Mifflin–St Jeor: 10 × kg + 6.25 × cm − 5 × years +5 for the male reference or −161 for the female reference. The study covered ages 19–78; above 78 is extrapolation. Five factors 1.2–1.9 give activity scenarios, not measured daily expenditure or validated weekly training counts. Energy estimates are not dietary prescriptions or predictions of weekly weight change.
Limits
Adults 20+, software height 50–300 cm equivalent, weight 1–1000 kg, optional positive waist up to 500 cm; energy age is a whole 20–120. These are software bounds, not medical validity ranges. Energy enabled requires a positive resting estimate. Unit conversion uses 1 in = 2.54 cm and 1 lb = 0.45359237 kg, rounded to six decimals. Decimal comma/point accepted. Pregnancy, children, ethnicity-specific BMI thresholds, clinical nutrition and measured body composition are not modelled.