Overview

This calculator returns the expected weight at a given gestational or postmenstrual age and sex for a specified percentile or z-score. It is intended for use in estimating dosing weights, setting growth targets, and understanding size-for-age context in the NICU.

Growth References

Fenton 2025 (22–36+6 weeks)

For ages 22+3 to 36+6 weeks, weights are derived from the Fenton 2025 Preterm Growth Chart LMS parameters. For more information, visit ucalgary.ca/fenton.

Fenton 2025 + WHO 2006 (37–50 weeks)

For ages 37+0 to 50+0 weeks, both Fenton 2025 and WHO 2006 Child Growth Standards results are displayed side by side. The clinician can compare both references and apply their own judgment based on the infant’s clinical context.

Important Notes

This calculator is intended as a clinical support tool for registered dietitians and other healthcare professionals. Reference weights are population-based estimates and should be interpreted in the context of the individual infant’s clinical history. This tool does not replace clinical judgment.

References

1. Fenton TR et al. Fenton 2025 Preterm Growth Chart. University of Calgary. ucalgary.ca/fenton. Used under CC BY-NC-ND 4.0.
2. WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: Methods and development. Geneva: World Health Organization, 2006.