worldofcalcsPregnancy Due Date Calculator 🤰
About This Calculator
This calculator uses Naegele's Rule to estimate your due date based on the first day of your last menstrual period (LMP). It also adjusts for your specific cycle length.
How is a due date calculated?
Your estimated due date (EDD) is 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). Pregnancy is counted from the period, not from conception, so at conception you are already about 2 weeks pregnant. This calculator also adjusts for cycles longer or shorter than 28 days and shows your current week, trimesters and key milestones.
Naegele's rule
Naegele's rule assumes a 28-day cycle with ovulation on day 14. A longer cycle means later ovulation, so the due date moves later by the same number of days; a shorter cycle moves it earlier. If you know the date of conception (for example after IVF), the due date is about 266 days after it.
Good to know
- Only about 1 in 20 babies arrives on the due date. Most are born between 37 and 42 weeks.
- An ultrasound in the first trimester, between 7 and 13 weeks, is the most accurate way to date a pregnancy. If it differs from your period-based date, your doctor will usually go by the scan.
- 37–38 weeks is early term, 39–40 weeks full term, 41 weeks late term and 42 weeks or later post-term.
- Book your first antenatal visit as soon as you know you're pregnant, and start folic acid if you haven't already.
- If your periods are irregular or you don't remember the date, the calculator can't be accurate. Use the date from your scan.
- This calculator is for information only and is not a substitute for advice from your doctor or midwife.
Worked example
- First day of last period: 1 January 2026, with a 28-day cycle
- Due date: 1 January + 280 days = 8 October 2026
- End of the first trimester (13 weeks): 2 April 2026
- Full term (39 weeks): 1 October 2026
- With a 32-day cycle, the due date moves 4 days later, to 12 October 2026
Pregnancy timeline
Key weeks counted from the first day of the last period, with dates for a period that started on 1 January 2026.
| Stage | Week | Date |
|---|---|---|
| Heartbeat can usually be seen on a scan | 6 | 12 February 2026 |
| First trimester ends | 13 | 2 April 2026 |
| First movements often felt (18–20 weeks) | 18 | 7 May 2026 |
| Baby may survive with intensive care if born now | 24 | 18 June 2026 |
| Second trimester ends | 26 | 2 July 2026 |
| Early term begins | 37 | 17 September 2026 |
| Full term begins | 39 | 1 October 2026 |
| Estimated due date | 40 | 8 October 2026 |
| Post-term; induction is usually advised | 42 | 22 October 2026 |
Timings vary from one pregnancy to another; your doctor's schedule may differ.