Pregnancy Calculator: Weeks, Months & Due Date (Complete Guide)
Many women feel confused about how to calculate pregnancy duration in weeks and months, especially during their first pregnancy. Should you count from ovulation or from your last menstrual period? What if your cycle is irregular? And can you calculate your due date like doctors do
In this guide, we explain everything in a simple and clear way, including a modern pregnancy calculator table
Pregnancy Duration in Weeks and Months
Pregnancy typically lasts
40 weeks-
9 calendar months + 1 week-
10 lunar months-
Calculation starts from the first day of your last menstrual period (LMP)-
Correct Way to Calculate Pregnancy
:Doctors calculate your due date using this formula
First day of last period + 7 days + 9 months
Example of Due Date Calculation
If your last period started on January 7:
+ 7 days → January 14
+ 9 months → October 14
Estimated due date: October 14
Pregnancy Calculator for Irregular Periods
If your cycle is irregular, the most accurate method is ultrasound between week 7 and week 13.
Mid-pregnancy scan → ± 1 week adjustment-
Late pregnancy scan → ± 2 weeks adjustment-
Pregnancy Calculation in IVF (ICSI)
Pregnancy Calculator Table (Weeks & Months)
| Pregnancy Month | Weeks |
|---|---|
| Month 1 | Week 1 – Week 4 |
| Month 2 | Week 5 – Week 8 |
| Month 3 | Week 9 – Week 13 |
| Month 4 | Week 14 – Week 18 |
| Month 5 | Week 19 – Week 22 |
| Month 6 | Week 23 – Week 26 |
| Month 7 | Week 27 – Week 30 |
| Month 8 | Week 31 – Week 35 |
| Month 9 | Week 36 – Week 40 |
Common Mistakes in Pregnancy Calculation
Conclusion
Using a pregnancy calculator correctly helps you track your baby’s growth and prepare for delivery. Always rely on medical guidance, especially if your cycle is irregular