Pregnancy Due Date Calculator
Enter your LMP to see your estimated due date, current week, and trimester milestones.
How Due Dates Work
Pregnancy is counted from the first day of your last menstrual period (LMP), not from conception. That's why it's said to last 40 weeks even though the baby grows for about 38. Add 280 days to your LMP and that's your estimated delivery date.
The Three Trimesters
- First trimester — Weeks 1–13: organ formation, highest miscarriage risk
- Second trimester — Weeks 14–27: "golden" trimester, movement begins
- Third trimester — Weeks 28–40: rapid growth, prep for delivery
This tool gives an estimate only. Always confirm with your doctor or OB/GYN.
Frequently Asked Questions
How is the due date calculated?
Naegele rule: last menstrual period (LMP) + 280 days (40 weeks). This assumes a 28-day cycle with ovulation on day 14 — the most common estimation method used globally.
How accurate is the LMP due date?
About 90% of babies arrive within ±2 weeks of the due date. First-trimester ultrasound dating is the most precise method — it can differ by a few days from LMP dating.
What if my cycle isn't 28 days?
Adjust by the difference: if your cycle is 32 days, add 4 days to the due date; if 26 days, subtract 2. Your doctor refines this at the first scan.
When can I take a pregnancy test?
Home tests detect hCG reliably from the first day of a missed period (about 14 days post-ovulation). Blood tests at a clinic can detect pregnancy 6–8 days after conception.