Gestational Age (Embryonic) Calculator
Calculate exact fetal age using LMP, Conception Date (IVF), or Ultrasound. Features a weekly milestone database and key development dates.
About
Precise dating of a pregnancy is critical for monitoring fetal growth and scheduling screenings. While standard "pregnancy wheels" assume a 28-day cycle and calculate from the Last Menstrual Period (LMP), this method can be inaccurate for women with irregular cycles or those undergoing IVF.
This calculator distinguishes between Gestational Age (clinical age, usually LMP-based) and Embryonic Age (actual age since fertilization). It offers specific modes for IVF (using transfer date or conception date) to provide the most accurate timeline possible. It also projects the Estimated Due Date (EDD) and current developmental milestones.
Formulas
The calculation depends on the input method. The standard term is 280 days (40 weeks).
If using LMP:
EDD = LMP + 280 days
If using Conception Date (Dcon):
EDD = Dcon + 266 days
Gestational Age (GA) in weeks:
GA = CurrentDate − (EDD − 280)7
Embryonic Age is calculated as GA − 2 weeks.
Reference Data
| Event | Gestational Age (Weeks) | Embryonic Age (Weeks) | Description |
|---|---|---|---|
| Fertilization | 2 | 0 | Sperm meets egg; zygote forms. |
| Implantation | 3 | 1 | Blastocyst attaches to uterine wall. |
| Neural Tube | 5 | 3 | Precursor to brain and spinal cord forms. |
| Heartbeat | 6 - 7 | 4 - 5 | Cardiac activity visible on ultrasound. |
| First Trimester End | 13 | 11 | Organogenesis complete; risk of miscarriage drops. |
| Viability | 24 | 22 | Potential survival outside womb. |
| Full Term | 39 - 40 | 37 - 38 | Ready for birth. |