When Did I Conceive? Use This Accurate Conception Date Calculator

✔ Find your exact conception date instantly
✔ Calculate due date and pregnancy week in seconds

Last updated: March 2026

Wondering when you got pregnant? This conception calculator helps you find your exact conception date based on your due date, ovulation, or last period.

Trusted by thousands of users for accurate pregnancy calculations

This tool is also useful as a pregnancy calculator to estimate conception date, ovulation timing, and due date accurately.

You can also use our pregnancy chance calculator to estimate your probability of getting pregnant.

Conception Date Calculator – Estimate When You Conceived

Trying to figure out when you conceived? This conception date calculator helps estimate the exact day you got pregnant using your due date, ovulation timing, or last menstrual period.

You can use this tool to:

To improve accuracy, you can also use our fertile window calculator to identify your most fertile days.

For fertility tracking, you may also want to use our Ovulation Calculator.

When Did I Get Pregnant?

Most women conceive during ovulation, which typically occurs about 14 days after the first day of the last menstrual period in a 28-day cycle.

This tool estimates your conception date so you can better understand your pregnancy timeline.

This conception calculator also works as a pregnancy calculator by helping you estimate due date, ovulation timing, and pregnancy week.

To understand your ovulation timing better, you can also use our ovulation calculator.

How This Conception Calculator Works

This calculator estimates conception timing using medically accepted pregnancy formulas. Depending on the information you enter, the calculation works in three ways:

1. Conception Date from Due Date

If you know your expected due date, the calculator subtracts 266 days (38 weeks) to estimate when fertilization likely occurred.

2. Conception Date from Last Menstrual Period

If you know the first day of your last menstrual period (LMP), the calculator estimates ovulation based on your cycle length and predicts the likely conception day.

3. Pregnancy Week from Known Conception Date

If you already know your conception date, the calculator adds 266 days to estimate your due date and calculates your current pregnancy week.

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

Related Tools

Ovulation Calculator

Calculate your most fertile days to increase chances of conception.
Due Date Calculator

Calculate your estimated due date based on your last menstrual period.
Pregnancy Week Calculator

Track your pregnancy progress week by week with important milestones.
Fertile Window Calculator

Identify your 6-day fertile window for optimal conception timing.
Pregnancy Chance Calculator

Estimate your probability of getting pregnant based on multiple factors.
Implantation Calculator

Predict when embryo implantation may occur after ovulation.

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.

Typical Pregnancy Timeline

Pregnancy Stage Average Timing
Ovulation Day 14 of a 28-day cycle
Conception (fertilization) Within 24 hours after ovulation
Implantation 6–12 days after ovulation
Positive pregnancy test 10–14 days after conception

When Did I Conceive?

Many pregnant women want to know exactly when conception occurred. While the precise moment of fertilization cannot always be determined, it can be estimated using your due date, ovulation date, or last menstrual period.

In most pregnancies, conception occurs about 14 days after the first day of the last menstrual period for a typical 28-day cycle. However, cycle length and ovulation timing can vary. For a more detailed fertility analysis, use our Pregnancy Chance Calculator or Implantation Calculator.

Calculate Conception Date From Due Date

Doctors estimate pregnancy length as 40 weeks from the first day of the last menstrual period or about 266 days from conception.

If you already know your due date, you can estimate conception by subtracting 266 days.

Example:

Example Conception Date Calculation

Due Date Estimated Conception Date
October 1, 2026 January 8, 2026
December 15, 2026 March 24, 2026
July 10, 2026 October 17, 2025

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.

When did I get pregnant if my due date is known?

If your due date is known, conception usually occurred about 266 days earlier. Doctors use this formula because pregnancy typically lasts 38 weeks from fertilization.

People Also Ask

Can I know the exact day I got pregnant?

The exact day of conception is difficult to determine because sperm can survive inside the reproductive tract for up to 5 days. Most calculators estimate the likely conception window based on ovulation timing.

Is conception the same as ovulation?

No. Ovulation is when the egg is released from the ovary. Conception occurs when sperm fertilizes the egg, usually within 12–24 hours after ovulation.

Can ultrasound determine conception date?

Early pregnancy ultrasound can estimate gestational age and approximate conception timing, but it cannot determine the exact moment of fertilization.

Related Pregnancy Calculators

Medical Disclaimer

This conception calculator provides estimates based on typical pregnancy timelines and menstrual cycle assumptions. It should not replace medical advice from a qualified healthcare professional.