Pregnancy Calculator & Week-by-Week Tracker
Track fetal development milestones, calculate your current pregnancy week, and estimate due date based on LMP. Includes size comparisons.
About
Understanding the timeline of pregnancy helps expectant parents prepare for critical health milestones. The medical standard for dating a pregnancy utilizes the First Day of the Last Menstrual Period (LMP). This method assumes conception occurred approximately 14 days into the cycle. While only an estimate, this timeline dictates when specific screening tests such as Nuchal Translucency or Anatomy Scans should occur.
Fetal development follows a predictable sequence. The embryonic stage transitions to the fetal stage at week 10. Viability outside the womb improves significantly after week 24. This tracker correlates calendar dates with these biological markers. It provides context for physiological changes such as the detection of a heartbeat or the first perception of fetal movement (quickening).
Formulas
The calculator uses Naegele's Rule for the Estimated Due Date (EDD). It adds one year, subtracts three months, and adds seven days to the LMP.
Current gestational age is derived by calculating the difference between the current date and the LMP.
Reference Data
| Trimester | Weeks | Key Developmental Milestones | Avg. Length (CRL/CHL) |
|---|---|---|---|
| First | 1−4 | Implantation, Neural Tube forms | 0.1 mm |
| First | 5−8 | Heartbeat detected, Limb buds appear | 1.6 cm |
| First | 9−13 | Major organs formed, Fingerprints | 7.4 cm |
| Second | 14−17 | Skeleton hardens, Sex distinguishable | 13 cm |
| Second | 18−22 | Movement felt, Hearing develops | 27 cm |
| Third | 28−40 | Lungs mature, Rapid weight gain | 50 cm |