Pregnancy Due Date Calculator: Weeks & Trimester Online
Estimate your due date, weeks of pregnancy and current trimester from the first day of your last period.
Estimate your due date from your last period using Naegele’s rule and see your current pregnancy week. Informational tool — it does not replace medical advice.
By VOV · Last updated: October 21, 2026
Guidance tool only — it does not replace medical advice. The due date is an estimate: only about 5% of babies are born on that exact date. Always consult your doctor.
Use cases
- Estimate your probable delivery date starting from the first day of your last menstrual period
- Calculate which pregnancy week you're in to know which ultrasound comes at your next appointment
- Discover your approximate date of conception to better understand your baby's current stage of development
Frequently asked questions
How is the due date calculated?
With Naegele’s rule: 280 days (40 weeks) are added to the first day of your last period. It is an estimate based on regular 28-day cycles.
How accurate is the due date?
It is a guide: only about 5% of babies are born on the estimated date. Being born between weeks 37 and 42 is normal.
What are the trimesters of pregnancy?
First trimester: weeks 1–13; second: weeks 14–27; third: weeks 28–40. Each stage has its recommended checkups.