Pregnancy Gestation by LMP and Ultrasound Biometry

Current Date   
Last Menstrual Period   
Ultrasound Estimation:
Ultrasound Date   
1st Trimester Measurement
Crown Rump Length
2nd and 3rd Trimester Measurements
Biparietal Diameter
Head Circumference
Gestation by LMP
Gestation by CRL
Gestation by BPD
Gestation by HC
  • This calculator gives you many options for estimating gestation and delivery dates. Input any or all parameters to compare the various date calculations. The Current Date is set to your local workstation date.
  • EDC by LMP is calculated by adding 280 days (40 weeks) to the first day of the last menstrual period.
  • Gestation by LMP is calculated from the first day of the last menstrual period.
  • Gestation by CRL is calculated: Weeks = 5.2876 + (0.1584 * Crown_Rump_Length) - (0.0007 * Crown_Rump_Length2). This will be gestation at time of ultrasound.
  • Gestation by BPD is calculated using the formula: Days = 2 * BPD + 44.2. This will be gestation at time of ultrasound.
  • Gestation by HC is calculated: Weeks = eTo(1.854 + (0.010451 * Head_Circumference) - (0.000029919 * Head_Circumference2) + 0.000000043156 * Head_Circumference3). This will be gestation at time of ultrasound.
  • N.B. CRL dates are appropriate for the first trimester, while BPD and HC dates are best applied to the second trimester.
  1. Mul T, Mongelli M, Gardosi J. A comparative analysis of second-trimester ultrasound dating formulae in pregnancies conceived with artificial reproductive techniques. Ultrasound Obstet Gynecol. 1996 Dec;8(6):397-402.
  2. Westerway SC, Davison A, Cowell S. Ultrasonic fetal measurements: new Australian standards for the new millennium. Aust N Z J Obstet Gynaecol. 2000 Aug;40(3):297-302.
  3. Altman DG, Chitty LS. New charts for ultrasound dating of pregnancy. Ultrasound Obstet Gynecol. 1997 Sep;10(3):174-91.
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