How to Calculate Conception Date
According to Naegele's Rule, the average human gestation period is 266 days. Therefore, to figure out the conception date from a birth date we need to subtract 266 days from the due date (or birth date).
But since it's difficult to subtract days from a calendar date without a date calculator, the easiest way to determine conception date by birth date manually is to count backward on a calendar.
Here is a conception calendar calculator that illustrates counting from 1 to 266 days backward from the due date.
How to Plan Baby Birth Date
If you select the desired due date in the Reverse Due Date Calculator on this page, the calculator will tell you when you will need to get pregnant to increase the odds of delivering on the desired date.
If you would rather know the month ranges, here is an at-a-glance chart showing target conception ranges for delivery months.
|Birth Month Conception Ranges|
|Plan||Conception Range (Mid)|
|January baby||Apr 10 - May 10 (Apr 24)|
|February baby||May 11 - Jun 7 (May 24)|
|March baby||Jun 8 - Jul 8 (Jun 21)|
|April baby||Jul 9 - Aug 8 (Jul 22)|
|May baby||Aug 9 - Sep 7 (Aug 21)|
|June baby||Sep 8 - Oct 7 (Sep 21)|
|July baby||Oct 8 - Nov 6 (Oct 21)|
|August baby||Nov 7 - Dec 7 (Nov 20)|
|September baby||Dec 8 - Jan 6 (Dec 21)|
|October baby||Jan 7 - Feb 6 (Jan 20)|
|November baby||Feb 7 - Mar 9 (Feb 21)|
|December baby||Mar 10 - Apr 9 (Mar 23)|
Of course, there is no guarantee whether or not your baby will be born on its due date. So the best chance for having the baby in the desired month is to plan conception in the middle of the ranges listed above.