Olsen 2015 BMI Calculator for Preterm Infants

Uses the 2015 Olsen BMI curves to report percentiles and Z-scores, from 24 - 41 weeks gestation.

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 Friday, December 6th, 2024

Parameters for BMI Calculation
Growth metrics on analysis date
Gender Male Female
Gestational age
Weight (grams)
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
  • Weight: grams are assumed. To enter pounds and ounces, enter #-#; e.g., 8-4 for 8 pounds and 4 ounces
  • Length: cm are assumed. To enter inches, enter #"; e.g., 20" for 20 inches

Based on