How to use the due date calculator
Enter the first day of your last menstrual period and your usual cycle length. The calculator estimates your due date, shows how many weeks and days pregnant you are today, and lists the key dates of each trimester.
Naegele's rule
Due date = first day of last period + 280 days + (cycle length − 28)
For example, if your last period started on January 1 and your cycle is 28 days, your estimated due date is October 8. With a 32-day cycle it moves 4 days later, to October 12.
Pregnancy milestones
- Weeks 1–13 (first trimester): the baby's organs form; many people have their first ultrasound.
- Weeks 14–27 (second trimester): often the most comfortable stretch; the anatomy scan happens around week 20.
- Weeks 28–40 (third trimester): the baby gains most of its weight. A pregnancy is considered full term from week 39.
This calculator gives an estimate for information only. Your doctor or midwife will confirm your due date, usually with an ultrasound.
