Conception Date Calculator

Determine when you likely conceived based on due date or last menstrual period

How Conception Date is Calculated

Conception Date = Last Menstrual Period + (Cycle Length - 14 days)

This standard calculation estimates when ovulation and conception likely occurred during your cycle.

Key Facts About Conception Dates:

  • Conception typically occurs 11-21 days after the first day of your last period
  • The due date based on conception is calculated as conception date + 266 days (38 weeks)
  • Our reverse due date calculator works backward from your due date to estimate conception
  • An accurate conception calculator like ours accounts for your individual cycle length

Pregnancy Timeline:

Event Timing Notes
Last Menstrual Period (LMP) Day 0 Pregnancy dating begins from first day of last period
Ovulation ~Day 14 (varies by cycle) Egg released, most fertile period
Conception ~Day 14-16 Sperm fertilizes egg, our conception date calculator estimates this
Implantation ~Day 20-24 Fertilized egg attaches to uterine wall
Due Date LMP + 280 days Our due date calculator conception tool can verify this

Medical Disclaimer

This conception date calculator is for informational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult with your physician or qualified healthcare provider regarding any questions you may have about your pregnancy. Dating scans (ultrasounds) provide the most accurate pregnancy dating, especially when performed in the first trimester.

How Our Conception Date Calculator Works

Choose Calculation Method

Select whether to calculate from your last menstrual period or from your due date. Our conception calculator handles both methods accurately.

Enter Your Dates

Provide either your last period date and cycle length or your due date. Our pregnancy conception calculator uses medical standards for calculations.

Get Detailed Results

Receive your estimated conception date, ovulation date, and due date with interpretation. Our conception date based on due date feature is especially helpful.

Understanding Conception Dates and Pregnancy Calculators

Determining your conception date is important for tracking pregnancy progress and estimating your due date. Our conception date calculator provides accurate estimates whether you know your last menstrual period or your due date.

How Conception Calculators Work

A conception calculator uses standard medical formulas to estimate when fertilization likely occurred. There are two main approaches:

  1. From Last Menstrual Period (LMP): Adds 14 days to LMP for 28-day cycles (adjusts for other cycle lengths)
  2. From Due Date: Our reverse due date calculator subtracts 266 days (38 weeks) from your due date

Why Conception Date Matters

Knowing your conception date based on due date or LMP helps with:

Ovulation vs. Conception

While our tool serves as both a conception calculator and ovulation date calculator, there are important differences:

Factor Ovulation Conception
Timing Day 14 of cycle (average) Within 24 hours of ovulation
Detection LH surge tests, basal temp Estimated by pregnancy conception calculator
Accuracy Can be precisely tracked Estimate only

Related Resources

For more information about conception and pregnancy dating, visit these authoritative resources: