Conception Date Calculator

Calculate when conception occurred or determine due date from conception date. Find your ovulation and fertilization timeline.

Conception Date Calculator

Choose your calculation method to find conception date or due date

When Was I Conceived?

Due Date

Enter your due date to calculate when conception occurred (due date - 266 days).

Key Features

Calculate conception date from due date, birth date, or LMP

Calculate due date from known conception date

Estimated ovulation window calculation

Multiple calculation methods for accuracy

Detailed calculation formulas and accuracy information

Understanding Conception

Conception: When sperm fertilizes the egg

Timing: Usually occurs during ovulation window

Duration: 266 days from conception to birth

Ovulation: Typically day 14 of 28-day cycle

Calculation Methods

Due Date Method

Most accurate: Due Date - 266 days

Birth Date Method

Retrospective: Birth Date - 266 days

LMP Method

Estimate: LMP + 14 days (ovulation)

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Frequently Asked Questions

When was I conceived?

To calculate when you were conceived, subtract 38 weeks (266 days) from your due date, or subtract 36 weeks (252 days) from your birth date. Our calculator does this automatically based on your input.

How do you calculate conception date?

Conception date can be calculated by subtracting 266 days from due date, or by adding 14 days to LMP (assuming ovulation on day 14). The calculator can also reverse calculate from birth date or due date.

What is the difference between conception date and ovulation date?

Conception date and ovulation date are typically the same or within 24 hours of each other, as fertilization usually occurs within 12-24 hours after ovulation when the egg is released.

How accurate is conception date calculation?

Conception date calculation is accurate within 1-2 days when based on early ultrasound dating or known ovulation date. It's less accurate when calculated from LMP due to cycle variations.

Can I calculate due date from conception date?

Yes, to calculate due date from conception date, add 266 days (38 weeks) to the conception date. This method is often more accurate than LMP-based calculations for women with irregular cycles.

Why is conception date important?

Knowing your conception date helps with accurate pregnancy dating, especially for women with irregular cycles. It's also useful for paternity determination and understanding fertility patterns.

Important Medical Disclaimer

This conception date calculator provides estimates only and should not replace professional medical advice.Conception timing can vary based on individual factors including cycle length, ovulation timing, and sperm survival. For accurate pregnancy dating and medical decisions, always consult your healthcare provider.