Pregnancy Week Calculator
Calculate your current pregnancy week and important milestones
Enter your date to calculate your pregnancy week
Understanding Pregnancy Weeks
Pregnancy is typically measured in weeks from your last menstrual period (LMP), not from conception. This is because:
- LMP is easier to remember than conception date
- It's the medical standard used worldwide
- Provides consistent dating across pregnancies
- Accounts for the full gestational period
Pregnancy Timeline
First Trimester: Weeks 1-12
Second Trimester: Weeks 13-26
Third Trimester: Weeks 27-40
Important Milestones by Week
Week 12
End of first trimester, reduced miscarriage risk
Week 20
Anatomy scan, halfway point
Week 24
Viability milestone
Week 37
Full-term pregnancy begins
How Pregnancy Weeks Are Calculated
The Standard Method: LMP Dating
Healthcare providers calculate pregnancy weeks from the first day of your last menstrual period (LMP). This method adds approximately 2 weeks to the actual time since conception, but it's the medical standard because:
- Most women remember their last period better than conception date
- It provides a consistent 40-week pregnancy timeline
- All medical guidelines and research use this method
- It accounts for the complete gestational period
Alternative Calculation Methods
Due Date Method
If you know your due date (from an ultrasound or previous calculation), you can work backwards to determine how many weeks pregnant you are.
Conception Date Method
If you know when conception occurred, add 2 weeks to get your gestational age. This accounts for the 2-week difference between LMP dating and actual conception.
Why Accurate Week Calculation Matters
- Medical appointments: Certain tests are done at specific weeks
- Fetal development: Track your baby's growth milestones
- Symptom timing: Understand what to expect when
- Birth planning: Know when you're considered full-term
- Work planning: Calculate maternity leave timing