Due Date Calculator
Estimated Due Date
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Current Week (if applicable)
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Conception Window
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Trimester Milestones
| Milestone | Week | Estimated Date |
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How the Due Date Calculator Works
This due date calculator estimates when your baby is expected to arrive using Naegele's Rule, the standard method used by healthcare providers worldwide. Whether you know the first day of your last menstrual period or your estimated conception date, this tool provides your estimated due date along with key trimester milestones.
When calculating from your last menstrual period (LMP), the calculator adds 280 days (40 weeks) and adjusts for your cycle length. If your cycle is longer than 28 days, the due date shifts later by the same number of extra days, since ovulation likely occurred later. When calculating from a conception date, 266 days (38 weeks) are added, as conception typically occurs about 2 weeks after the LMP.
The milestones table highlights important dates throughout pregnancy: the end of each trimester, when you might hear the first heartbeat (week 6), the nuchal translucency scan (week 12), the anatomy scan (week 20), the viability threshold (week 24), full-term status (week 37), and your estimated due date (week 40). Remember that only about 5% of babies arrive on their exact due date. Most births occur within a two-week window around the estimated date, and your healthcare provider may adjust your due date based on ultrasound measurements.