How is the due date calculated?
Using Naegele's rule: 280 days (40 weeks) from the first day of your last menstrual period. The conception date is estimated at about 14 days after the start of your last period.
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Pregnancy Week Calculator
Track all 40 pregnancy weeks, compute the estimated due date, trimester, and the ISO week of the due date — bilingual, no signup.
- You are at
- 8 weeks 0 days (First trimester)
- Estimated due date
- Thursday, March 25, 2027
- Conception date (estimated)
- Thursday, July 2, 2026
- Days remaining
- 224 (32 wk)
- ISO week of due date
- Week 12 · 2027
Four-week milestones
| Week | Date | Trimester |
|---|---|---|
| 4 | Thursday, July 16, 2026 | First trimester |
| 8 | Thursday, August 13, 2026 | First trimester |
| 12 | Thursday, September 10, 2026 | First trimester |
| 16 | Thursday, October 8, 2026 | Second trimester |
| 20 | Thursday, November 5, 2026 | Second trimester |
| 24 | Thursday, December 3, 2026 | Second trimester |
| 28 | Thursday, December 31, 2026 | Third trimester |
| 32 | Thursday, January 28, 2027 | Third trimester |
| 36 | Thursday, February 25, 2027 | Third trimester |
| 40 | Thursday, March 25, 2027 | Third trimester |
Estimate based on Naegele's rule (280 days / 40 weeks from last menstrual period). Not medical advice — consult your healthcare provider.
How it works
Pick one of three modes (last period, due date, conception). We apply Naegele's rule: 280 days = 40 weeks. You get the current gestational age, due date, trimester, four-week milestones, and the ISO 8601 week number of the due date.
Frequently asked questions
How many weeks is a full-term pregnancy?
A full-term pregnancy lasts 40 weeks (280 days) measured from the last menstrual period. Births between 37 and 42 weeks are considered full-term.
What are the trimesters?
First trimester: weeks 1–12. Second trimester: weeks 13–26. Third trimester: weeks 27–40.
What's the ISO week of my due date?
The result shows the ISO 8601 week number of the due date — useful for aligning maternity leave, team scheduling, and logistics.
Is this medical advice?
No. This tool only provides estimates. For precise dating, consult your healthcare provider — first-trimester ultrasound remains the gold standard.