Pregnancy Weeks Calculator
Calculate weeks pregnant
Formula
Weeks = Days since LMP ÷ 7
Full term = 40 weeks
Pregnancy Milestones
| First trimester | Weeks 1-12 |
| Second trimester | Weeks 13-26 |
| Third trimester | Weeks 27-40 |
| Full term | 39-40 weeks |
Related
Complete Guide to Pregnancy Weeks Calculator
Pregnancy is measured in weeks from the first day of your last menstrual period (LMP), not from conception. This is gestational age.
How Weeks Are Counted
You are 4 weeks pregnant when you miss your period, even though conception occurred about 2 weeks earlier. This dating system is universal in medical care.
Trimester Breakdown
- First (1-12): Major organ development
- Second (13-26): Growth and movement felt
- Third (27-40): Final growth and preparation
Frequently Asked Questions
From the first day of your last menstrual period, not conception. You are 2 weeks pregnant at conception and 4 weeks when you miss your period.
Medical convention uses LMP because it is a known date. Exact conception date is usually unknown. This system is standard worldwide.
First: weeks 1-12. Second: weeks 13-26. Third: weeks 27-40. Each has different developmental milestones and symptoms.
Not quite. 40 weeks is about 9 months and 1 week. The 9 months figure is an approximation that has stuck in popular culture.
Early ultrasounds (8-12 weeks) can adjust dating. If there is more than 7 days difference from LMP calculation, doctors may change your due date.
Full term is 39-40 weeks. Early term is 37-38 weeks. Late term is 41 weeks. Post-term is 42+ weeks.
It assumes a 28-day cycle with ovulation on day 14. If your cycles are irregular, ultrasound dating is more accurate.