What is a conception date?

Your conception date is the date your baby was conceived (sounds simple enough, right?). 

And guess what? You can use your conception date to find out your baby’s due date. Just add 266 days (aka 38 weeks or 9 ½ months) to your conception date to get the answer in the form of your estimated due date.

But contrary to popular opinion, your conception date is not necessarily the same as the day you had sex when you were trying to get pregnant. 

If you're a little confused about how that could be the case, read on to find out more about your conception date when planning for your cute new addition.

How do you calculate your conception date?

You might want to grab your calendar, calculator and notepad if you don't already have them handy for this ... You can figure out your conception date by adding a typical range of 11 to 21 days to the first day of your last period. The day you conceive your baby will depend on how often you get your period.

How accurate is your conception date?

Your conception date isn’t always that accurate and can be difficult to pinpoint. Sperm can be viable for several days and an egg can be fertilized up to 24 hours after ovulation, so it’s hard to zero in on exactly when conception occurred. 

That’s why doctors are more likely to use the first day of your last menstrual period (LMP) rather than your conception date to figure out your due date.

Is your conception date the same as your ovulation date?

No, your conception date isn’t the same as your ovulation date. 

Your ovulation date is the day or days that you ovulate, which usually happens about two weeks (or 14 days) after the first day of your cycle, lasting for a few days. Your conception date is the day when the egg is fertilized by sperm.

Can you predict your conception date?

Yes! You can predict your conception date by calculating when you’ll be ovulating and what your fertile window will be. 

Remember that ovulation generally occurs about two weeks after the first day of your period (though everyone is different), but the LH surge that triggers ovulation may last for one to two days. 

Your fertile window usually starts a couple of days before you ovulate and lasts until about a day after ovulation. 

You can predict your conception date as being one of those days in your fertile window. Count seven to 10 days from the last day of your period to pinpoint the stretch of time when you’re most fertile and are likely to conceive.

It's also worth noting that this tool isn't meant to replace anything your doctor or midwife tells you. Always have your pregnancy doctor or other practitioner confirm your pregnancy and due date as soon as possible. In the meantime, have fun with this Conception Date Calculator and our other pregnancy tools, and let the planning and the countdown begin!