What is the difference between conception date and due date?

Conception date is when the egg was fertilized (usually around day 14-15 of your cycle). Due date (estimated delivery date) is calculated as 280 days (40 weeks) from the first day of your last menstrual period (LMP). Due date is about 2 weeks after conception.

How accurate is this pregnancy calculator?

This calculator provides estimates based on standard pregnancy calculations (280 days from LMP). Accuracy depends on regular cycles. Ultrasound dating in the first trimester is most accurate (±3-5 days). This calculator should not replace medical advice from your healthcare provider.

What is the luteal phase and why does it matter?

The luteal phase is the period after ovulation until your next period (typically 10-16 days). It matters because conception date is calculated based on this timing. Knowing your luteal phase helps calculate a more accurate conception date, especially if your cycle length varies.

How many weeks am I if I just found out I'm pregnant?

Pregnancy is counted from the first day of your last menstrual period, not from conception. Most women discover pregnancy around 4-5 weeks. Use your LMP date to calculate your exact pregnancy week using this calculator.

What happens during each trimester?

First trimester (weeks 1-13): Organ development, morning sickness common. Second trimester (weeks 14-26): Increased energy, fetal movement felt, baby gains size. Third trimester (weeks 27-40): Rapid growth, preparation for birth, increased discomfort possible.

Why do only 5% of babies arrive on their due date?

Due dates are estimates with a range of normal delivery between 37-42 weeks. Babies vary in development, and many factors affect delivery timing including cycle length variation, conception date variations, and individual differences.

Can I use this if I have irregular cycles?

This calculator works best with regular cycles. If you have irregular cycles, use an ultrasound date from your first trimester for most accurate dating. You can still use this tool for general estimates, but consult your healthcare provider.

What if I don't know my exact due date or LMP?

If you don't know your exact due date or LMP, your healthcare provider can perform an ultrasound (especially accurate in first trimester within ±3-5 days) to establish accurate pregnancy dating. Use that ultrasound date for this calculator.

Pregnancy Conception Calculator

Estimate Your Conception Date & Pregnancy Progress

Calculate your conception date based on your due date or last menstrual period (LMP). This calculator helps you determine when you likely conceived based on standard pregnancy calculations.

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Average Cycle Length (days)

Enter cycle length between 21-35 days

Luteal Phase Length (days)

Enter luteal phase length between 10-16 days

Expected Due Date

Your Results

Enter your details and click "Calculate" to see your pregnancy information here.

Understanding Pregnancy Conception

How Pregnancy is Dated

Pregnancy is counted from the first day of your last menstrual period (LMP), not from the conception date. This is why a pregnancy is typically 280 days or 40 weeks long. Your due date is calculated as 280 days after your LMP.

When Conception Occurs

Conception typically occurs around day 14 of a 28-day cycle during ovulation. Sperm can live 3-5 days in the reproductive tract, so conception can occur up to 5 days before ovulation. The fertile window is usually 5 days before ovulation through the day of ovulation.

Conception Timeline

Event	Timing (Days)	Description
LMP	Day 1	First day of last menstrual period - pregnancy dating begins here
Ovulation	Day 14	Egg is released from ovary (varies based on cycle length)
Fertilization	Day 14-15	Sperm meets egg - conception occurs
Cell Division	Day 15-17	Fertilized egg (zygote) divides as it travels to uterus
Implantation	Day 21-24	Fertilized egg implants in uterine lining - pregnancy establishes
HCG Detection	Day 25-28	Human chorionic gonadotropin (HCG) hormone detectable in blood/urine

Important Medical Disclaimer

This pregnancy calculator provides educational estimates only. Conception and pregnancy dates are calculations based on standard models and your input. Results should not be considered medical advice. Ultrasound dating, especially in the first trimester, is more accurate than calculations. Always consult with your healthcare provider for accurate pregnancy dating, medical concerns, or complications. This calculator is for information and tracking purposes only, not for medical diagnosis or treatment.

Quick Tips

Track your cycle: Know your typical cycle length for accurate calculations
First trimester ultrasound: Most accurate dating method (±3-5 days)
Due dates are estimates: Only ~5% of babies arrive on exact due date
Know your luteal phase: Affects ovulation timing and conception date
Regular prenatal care: Essential for healthy pregnancy monitoring

Related Health Tools

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Conception & Fertility:

Important Note

This calculator provides educational estimates for pregnancy tracking. Results should supplement, not replace, professional medical care. Always consult with your healthcare provider about pregnancy dating, concerns, or medical decisions.

Pregnancy Conception Calculator

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