Pregnancy Due Date Calculator
Calculate your estimated due date, conception date, and how many weeks pregnant you are — instantly and for free.
Due Date Calculator
* Based on Naegele's rule (LMP + 280 days). Actual delivery dates vary. Always confirm with your OB/GYN.
Track your menstrual cycle to better predict fertile windows and plan for pregnancy.
Start Tracking My CyclePregnancy Timeline at a Glance
| Trimester | Weeks | Key Milestones |
|---|---|---|
| First Trimester | Weeks 1–12 | Implantation, major organ development, heartbeat detectable at ~6 weeks |
| Second Trimester | Weeks 13–26 | Baby movements felt, gender reveal possible, significant growth |
| Third Trimester | Weeks 27–40 | Rapid weight gain, lung maturation, preparation for birth |
Due Date Calculator FAQs
How is a due date calculated?
A pregnancy due date is calculated using Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on Day 14. Your OB/GYN may adjust the due date based on early ultrasound measurements.
How accurate is a due date calculator?
Due date calculators based on LMP are an estimate. Only about 5% of babies are born on their exact due date. The actual delivery window for a full-term pregnancy is 37–42 weeks. An early ultrasound (6–14 weeks) provides the most accurate dating.
What is considered full-term pregnancy?
A full-term pregnancy is 39–40 weeks. Early term is 37–38 weeks, late term is 41 weeks, and post-term is 42+ weeks. Deliveries before 37 weeks are considered preterm.
Can I calculate a due date from conception date?
If you know your conception date, add 266 days (38 weeks) to get your estimated due date. Conception typically occurs around Day 14 of a 28-day cycle, approximately 2 weeks after the last period started.
What if my cycle is not 28 days long?
If your cycle is longer than 28 days, ovulation (and conception) happened later, pushing your due date forward. If shorter, your due date is earlier. Your healthcare provider will adjust the due date calculation based on your cycle and early ultrasound.