When Did I Conceive?

Just found out you’re pregnant and wondering when it happened? You’re definitely not alone. Whether you're thinking about who the father might be or just trying to understand your timeline, we're here to help. Need answers now? You can text a nurse anonymously—for free— 760-965-7513.
The truth is, there’s no way to pinpoint the exact moment of conception. Unlike your period, which comes on a clear schedule, conception is a bit more behind-the-scenes. But the good news? You can estimate it pretty closely by knowing a few things about your cycle.
What Date Did I Conceive?
No matter how far along you are—2 weeks or 20—there’s a way to make an educated guess about when you got pregnant.
Here’s what we know:
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Most people ovulate about 14 days after the first day of their last period.
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You’re most likely to get pregnant during the 2–3 days around ovulation.
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Sperm can live inside the body for up to five days, meaning sex before ovulation can still result in pregnancy.¹ ²
So, if you know the first day of your last period and the average length of your cycle, you can estimate your conception window using a basic formula or an online tool.
Conception Date Calculator
By calculating the time since your last period, you can get a rough idea of your ovulation window and, hence, when you conceived.
If you're not a fan of doing the math yourself, there are free online calculators like the one below, or you can text us at 760-965-7513. One of our nurses can help you figure it out.
Keep in mind: Everybody is different. Some people ovulate earlier, later, or for longer than average. So while a calculator gives you a good idea, it’s not 100% exact.
Conception Calculator
Conception Date from Ultrasound
Another way to determine the conception date is through an ultrasound. Fetuses tend to grow at a consistent rate, which means the age of the fetus can, quite literally, be measured. As such, an ultrasound can give a more accurate date range than an ovulation calculator.
Having an ultrasound not only helps you know when you conceived but can also confirm the health and viability of the fetus, ensuring that the pregnancy has not miscarried and is not ectopic.3
You can have an ultrasound performed at your local OBGYN office; however, there’s usually paperwork and billing involved. Alternatively, your local pregnancy center may be able to offer free ultrasound services without the need for hospitals or insurance companies to get involved.
Get Help Determining Your Conception Date
If you need help figuring out which day you conceived or if you have any questions about pregnancy in general, we’re here to help.
Simply send a text to 760-965-7513 and get a real certified nurse to answer your questions and walk you through your options.
Sources:
1. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/expert-answers/ovulation-signs/faq-20058000
2. https://my.clevelandclinic.org/health/articles/23439-ovulation
3. https://my.clevelandclinic.org/health/diagnostics/9704-ultrasound-in-pregnancy