Due Date Calculator
Calculate your pregnancy due date and track important milestones. Choose your calculation method below.
This is the most common method used by healthcare providers.
Pregnancy Resources
These are external links to trusted pregnancy and parenting resources.
How to Calculate Your Due Date
The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is the same calculation your doctor uses.
Because conception typically happens about 14 days after LMP, the actual pregnancy is approximately 38 weeks from conception, even though it's tracked as 40 weeks from LMP.
Keep in mind that a due date is an estimate — only about 5% of babies are born on the exact due date. Most arrive within a ±2-week window.
Pregnancy Timeline
• First Trimester (Weeks 1–12): Major organ development begins. Morning sickness is common. The heartbeat can be detected around week 6. By week 12, all major organs and body structures have formed.
• Second Trimester (Weeks 13–26): Often called the "honeymoon phase." Energy returns, nausea typically subsides. You'll feel the first kicks (16–22 weeks). The anatomy scan at 20 weeks checks the baby's development in detail.
• Third Trimester (Weeks 27–40+): Baby gains weight rapidly. More frequent prenatal visits. The baby is considered "full term" at 37 weeks. Nesting instincts may kick in as you prepare for arrival.
Important Pregnancy Milestones
| Week | Milestone | Significance |
|---|---|---|
| 6 | First Heartbeat | Heartbeat visible on ultrasound |
| 8 | First Prenatal Visit | Confirm pregnancy, initial blood work |
| 12 | End of 1st Trimester | Miscarriage risk drops significantly |
| 20 | Anatomy Scan | Detailed ultrasound, gender reveal possible |
| 24 | Viability | Baby could survive with medical intervention |
| 28 | 3rd Trimester | Final phase begins, more frequent visits |
| 37 | Full Term | Baby is ready for birth |
| 40 | Due Date | Estimated date of delivery |
| 41–42 | Post-Term | Provider may recommend induction |
Due Date Accuracy
• Only ~5% of babies are born on the exact due date.
• Most babies are born between 37 and 42 weeks.
• First-time mothers tend to deliver a few days later than their due date on average.
• Early ultrasounds (before 12 weeks) provide the most accurate dating, with a margin of error of about ±5 days.
• Factors like maternal age, weight, genetics, and whether it's a first pregnancy can all influence when labor begins.