HAZ Calculator - Height-for-Age Z-Score (Stunting)
Calculate height-for-age z-score (HAZ) for children 0–60 months using WHO Child Growth Standards. Identify stunting, severe stunting, and normal growth.
The height-for-age z-score (HAZ) is the standard indicator for childhood stunting - chronic undernutrition that has caused a child to be too short for their age. Unlike wasting, which reflects acute malnutrition, stunting accumulates over months and years, with the most critical window running from conception to 24 months of age. HAZ is calculated using the WHO Child Growth Standards LMS method, which accounts for the slightly skewed distribution of child measurements by applying a Box-Cox power transformation. A child with a HAZ below −2 is classified as stunted; below −3, as severely stunted. The calculator uses WHO reference medians (M), Box-Cox power (L), and coefficient of variation (S) for each month of age and sex.
Measurement note: Children under 24 months are measured lying down (recumbent length); children 24 months and older are measured standing (height). Recumbent length is approximately 0.7 cm greater than standing height - use the correction checkbox below if your measurement method differs from the standard for the child’s age.
| Z-score | Classification | Action |
|---|---|---|
| ≥ −2 | Normal growth | Routine monitoring at scheduled visits. |
| < −2 and ≥ −3 | Stunted (moderate) | Investigate dietary history, infections, and feeding practices. Enrol in nutrition-sensitive programme and increase monitoring. |
| < −3 | Severely stunted | Refer for comprehensive assessment. Evaluate for underlying disease, social factors, and micronutrient deficiencies. Intensive nutrition rehabilitation. |
Source: WHO Multicentre Growth Reference Study Group (2006). WHO Child Growth Standards: Length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age: Methods and development. Geneva: World Health Organization. LMS parameters from WHO IGROWUP software package.