Accurate Conception Date Calculator – Find When You Conceived

Enter your due date, last period (LMP), or known conception date to estimate when you conceived, your due date, or how far along you are.

Calculate Due Date or Pregnancy Week from Conception Date

If you know the day you conceived (e.g., from ovulation tracking or fertility treatment), enter it above to instantly see your estimated due date and current pregnancy week.

Conception Date Calculator

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How to Calculate Your Conception Date

If you're wondering "When did I conceive?", here's how to estimate it accurately using medical guidelines and your known dates.

From Your Due Date

If you know your due date, subtract 266 days (38 weeks) to estimate conception:

Conception Date = Due Date - 266 days

This is because pregnancy is typically 266 days from conception to birth.

From Your Last Menstrual Period (LMP)

Conception usually occurs about 11–21 days after the first day of your last period:

Conception Date = LMP + (Cycle Length - 14)

For a 28-day cycle, ovulation (and likely conception) happens around day 14.

Understanding the 6-Day Fertile Window

Conception can occur within a 6-day fertile window:

This is why the exact conception date might vary by a few days.

Factors Affecting Accuracy

Your actual conception date may differ due to:

For the most accurate dating, early pregnancy ultrasounds are recommended.

Frequently Asked Questions

How precise is this estimation?

The conception date estimation is based on standard calculations and assumptions about regular menstrual cycles. It provides a good approximation but isn't exact. Sperm can survive up to 5 days, and ovulation can vary from the expected date, so the actual conception date might differ by a few days.

How long after conception can a pregnancy test detect pregnancy?

Most home pregnancy tests can detect pregnancy about 10-14 days after conception, which is typically around the time of a missed period. Some sensitive tests claim to work a few days before a missed period, but waiting until after a missed period generally provides more accurate results.

Can implantation make the date later?

Yes, conception refers to fertilization, but implantation (when the fertilized egg attaches to the uterine wall) occurs several days later, typically 6-12 days after conception. Pregnancy tests detect the hormone hCG produced after implantation, not at the moment of conception.

What if I used fertility treatment?

If you've undergone fertility treatments like IVF, the conception date might be more precisely known. In IVF, conception occurs when the embryo is fertilized in the lab, and the transfer date is documented. This calculator may not be accurate for assisted reproductive technology cases.

Why does conception date matter?

The conception date helps healthcare providers track fetal development, determine accurate gestational age, and plan appropriate prenatal care. It's also useful for personal records and understanding your pregnancy timeline.

How to calculate date of conception?

If you know your due date, subtract 266 days. If you know your last menstrual period (LMP), add your cycle length minus 14 days.

How far along would I be if I conceived on a certain date?

Pregnancy is counted from conception. If you conceived on [date], your due date is approximately 266 days later, and your current pregnancy week is (today - conception date) ÷ 7.

Can I know the exact day I got pregnant?

Not usually. Conception can occur within a 6-day fertile window. Exact dates are only known with fertility tracking or assisted reproduction like IVF.

How accurate is a conception date calculator?

It's accurate for people with regular cycles. Irregular cycles, late ovulation, or fertility treatments can shift the actual date. Early ultrasounds are more precise.

How many days after my period can I get pregnant?

If you have a 28-day cycle, ovulation typically occurs around day 14. Since sperm survive up to 5 days, you could conceive as early as day 9—just a few days after a 5-day period ends.

Is the conception date the same as ovulation date?

Not exactly. Ovulation is when the egg is released. Conception (fertilization) usually happens within 12–24 hours after ovulation. So they're often on the same day or within 1 day.