UKMedCalc

For healthcare professionals. Educational tool only — not a medical device. Verify all results against the current BNF, NICE guidance and local policy, and apply clinical judgement.

Body size

Body Mass Index (BMI)

Calculates BMI with WHO weight categories, plus the healthy weight range for the given height.

kg
cm
Enter the required values to see the result.

Formula

BMI=weight (kg)height (m)2\text{BMI} = \frac{\text{weight (kg)}}{\text{height (m)}^2}

Caveats & limitations

  • A screening tool, not a body-composition measure: muscular individuals, pregnancy, oedema and age-related muscle loss distort interpretation.
  • Adult categories do not apply to children — use age- and sex-specific BMI centile charts.
  • Ethnicity-specific thresholds differ (see UK note).

Evidence & UK guidance

Primary evidence

  • World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. Geneva: WHO; 2000.

    Source

UK practice

WHO categories as applied in NICE guidance. NICE NG246 (2025, replacing PH46) sets lower thresholds for adults from South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds: overweight is BMI 23–27.4 and obesity ≥27.5 kg/m² (obesity class thresholds reduced by 2.5). In children, use BMI centile charts rather than adult categories.

Official resources

Formula and citations last verified: 2026-08-03

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