Neonatal Ponderal Index (Rohrer’s Index)
Neonatal ponderal index: 100 × birth weight (g) / length (cm)³; a value below ~2.0 marks disproportionate wasting (asymmetric intrauterine growth restriction).
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Birth weight
- 2200 g
- Length
- 50 cm
Result: Ponderal index 1.76 — below 2.0 (disproportionate wasting, asymmetric IUGR).
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Bands
- Neonatal normal ≈ 2.0–3.0; < 2.0 in a term infant signals disproportionate wasting (asymmetric IUGR), more specific than birth-weight-for-age; > 3.0 is heavy-for-length.
What you enter
- Birth weight
- Length
How this is calculated
- Formula
- PI = [weight (g) / length (cm)³] × 100, the proportionality of weight to length at birth.
Miller HC, Hassanein K. Diagnosis of impaired fetal growth in newborn infants. Pediatrics. 1971;48(4):511-522. Validation: Fay RA, et al. Ponderal index: a better definition of the "at risk" growth-restricted group. Aust N Z J Obstet Gynaecol. 1991;31(1):17-19. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.