Olsen 2010 Growth Calculator for Preterm Infants

Uses the 2010 Olsen growth charts to report percentiles and Z-scores.

Now with integrated gestational age calculator and decision support (e.g., retinopathy of prematurity, RSV prophylaxis).

Citing: If you use PediTools for a publication or clinical guideline, please consider citing: Chou JH et al., J Med Internet Res 2020;22(1):e16204 (available open access [PDF])




Today is Saturday, September 27th, 2025

Growth Parameters
Growth metrics on analysis date
Gender Male Female
Gestational age
Weight (grams)
Head circumference (cm)
Length (cm)

Last menstrual period
Due date
Date of birth
Gestation at birth
Analysis date
Age in days on date
Day of life on date
Reset form

Tips and Tricks

  • Enter the bare minimum information
    • can enter just gender, gestational age, and growth metrics, without dates, if desired
    • if only a gestational age is entered, the 50th percentile values will be displayed
    • if any dates are entered, all other dates will be deduced, if possible
  • Gestational age, enter in the form of ## #/7; e.g., 30 3/7 for 30 weeks and 3 days gestation
    • The Olsen 2010 paper reports measures for completed weeks of gestation -- i.e., from 23 0/7 through 23 6/7 weeks is considered 23 weeks completed gestation
    • In this program, the weeks gestation + 3/7 weeks (the median between 0 and 6 days) will yield the same results as the paper
  • Weight: grams are assumed. To enter pounds and ounces, enter #-#; e.g., 8-4 for 8 pounds and 4 ounces
  • Head circumference or length: cm are assumed. To enter inches, enter #"; e.g., 20" for 20 inches

Based on