Gestational age calculator for preterm infants

Enter any available dates, ages, or gestations, and other values will be calculated.

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, October 5th, 2024

Gestational Age Calculator
Last menstrual period
Due date
Date of birth
Gestational age at birth
Date of Interest
Age in days on Date
Day of life on Date
Postmenstrual age
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Instructions and notes:

  • Enter any known values. All possible other values will be calculated. Values that can not be calculated will be left blank.
  • Dates are interpreted semi-intelligently, but be aware of possible errors if unrecognized formats are used.
  • The due date is 40 weeks after the last menstrual period, or 38 weeks after conception (implantation / fertilization).
  • On the date of birth, a baby is on the first day of life (day of life 1), but is zero days old.
  • The first exam for retinopathy of prematurity is at 31 weeks postmenstrual age, but not before 4 weeks of age (typically indicated if born at <31 weeks gestation or birth weight <1,500 grams).