Pregnancy Due Date Calculator
Estimate your pregnancy due date from either the first day of your last menstrual period (Naegele’s rule: +280 days) or the date of conception (+266 days). See your current gestational age in weeks and days, current trimester and how many days remain until the estimated due date. All processing runs locally in your browser.
How to use
- 1
Pick a calculation method
Choose “Last menstrual period” (default) or “Conception date”. Switching modes carries the equivalent date across so you don’t lose your entry.
- 2
Enter the date
Type or pick the LMP or conception date. The date cannot be in the future. The due date is computed from this single input.
- 3
Read the estimated due date
The big number shows the estimated due date with the number of days remaining (or overdue). Gestational age, trimester and the equivalent LMP / conception date are listed below.
- 4
Copy or share the summary
Use Copy to put a one-line summary on your clipboard. Discuss the result with your healthcare provider — this tool is for informational purposes only.
Common use cases
- Get a quick first-pass due date before your first prenatal appointment.
- Track your current gestational week and trimester as the pregnancy progresses.
- Plan maternity leave, baby shower or nursery milestones around the estimated date.
- Cross-check the date from an ultrasound scan against the LMP-based estimate.
Limitations
Estimate only — consult your healthcare provider. This tool provides a statistical estimate based on a 28-day cycle with ovulation on day 14. It does not account for cycle-length variation, irregular cycles, IVF transfer dates, multiple pregnancies or medical history. Ultrasound dating in the first trimester is more accurate and should override this estimate. Always consult a qualified healthcare professional for medical advice.
- Naegele's rule assumes a 28-day cycle. If your cycles are longer or shorter, the LMP-based estimate may be off by several days — a dating ultrasound is more accurate.
- Gestational age is counted from the LMP, not from conception. A “40-week” pregnancy corresponds to ~38 weeks from fertilisation.
- Trimester boundaries follow the common convention: 1st = weeks 1–12, 2nd = weeks 13–27, 3rd = weeks 28–40. Some clinicians use slightly different cutoffs.
- Only about 5% of babies are born on their estimated due date; the normal delivery window is 37–42 weeks.