Pregnancy Calculator
Get a complete pregnancy timeline including due date, trimester boundaries, conception date and weekly milestones — calculated from your last menstrual period (LMP) or conception date.
How to use the Pregnancy Calculator
- Enter your inputs into the Pregnancy Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The Naegele's rule
Due date = LMP + 280 days (40 weeks) · · · or Conception date + 266 days (38 weeks)
The standard method assumes a 28-day cycle with ovulation on day 14. Adjustments apply for known cycle length variations. Trimesters: first 0–13 weeks, second 14–27 weeks, third 28–40+ weeks.
Worked example
LMP date: January 15. Due date: January 15 + 280 days = October 22. Conception date: about January 29. End of first trimester: April 15. End of second trimester: July 22.
Frequently asked questions
How accurate is the due date?
Only about 4–5% of births occur on the exact due date. Most occur within ±2 weeks. An ultrasound dating in early pregnancy is more accurate than LMP-based dating.
What if my cycle is not 28 days?
Adjust by adding or subtracting the difference from 14 days of ovulation. A 32-day cycle would push estimated conception to day 18, and add 4 days to the due date.
How do "weeks pregnant" get counted?
Pregnancy weeks are counted from LMP, not conception. So at 4 weeks pregnant, conception was only about 2 weeks ago. It's confusing but it's the medical standard.