BMI calculator
Body Mass Index in centimetres/kilograms or feet/stone, calculated as you type. If your BMI lands in the range where weight-management treatments can be considered, you'll see the next step.
What the BMI categories mean
- Below 18.5 — underweight. Weight-loss medicines aren't appropriate; nutrition support is.
- 18.5–24.9 — healthy weight. No medicine pathway here.
- 25.0–29.9 — overweight. GLP-1 medicines may be considered only if you have a related condition (type 2 diabetes, hypertension, etc.). Lifestyle support is the first line.
- 30.0–34.9 — Class I obesity. GLP-1 weight-management medicines can be considered after a full video consultation with our Independent Prescribing pharmacist.
- 35.0–39.9 — Class II obesity. Same medicine pathway, with a stronger clinical case.
- 40.0+ — Class III obesity. Private GLP-1 pathway available; we'd also recommend asking your GP about NHS bariatric services.
What BMI doesn't measure
- Muscle mass — athletes and bodybuilders often classify as "overweight" by BMI but aren't.
- Body composition — fat distribution matters (visceral fat carries more risk than subcutaneous).
- Ethnicity — lower BMI thresholds apply for some groups (e.g. people of South Asian, Chinese, or Black African heritage may face health risks at BMI ≥ 23 / ≥ 27.5).
- Age — BMI is calibrated for adults; different metrics apply for children and over-65s.
The pharmacist accounts for all of this at the consultation. BMI is a starting screen, not a verdict.