Pregnancy Conception Calculator

Estimate your conception date based on due date or last menstrual period.

Result

Fill in the fields above, then press Calculate.

A conception calculator estimates when conception likely occurred based on your due date or last menstrual period.

Select whether you know your due date or last menstrual period date. Enter the date, and the calculator will estimate the probable conception date range and fertile window.

Examples

Due date of October 8

If your due date is October 8, probable conception occurred around January 14-18, with the most likely date being January 16.

Frequently Asked Questions

Why is conception date a range and not exact?
Ovulation timing varies between women and even between cycles. Sperm can also survive up to 5 days inside the body, so intercourse several days before ovulation can result in conception.
Can I determine paternity from the conception date?
While the conception window can narrow down timing, it is not precise enough for paternity determination. DNA testing is the only reliable way to establish paternity.
Related Calculators
Conception Calculator
Due Date Calculator
Ovulation Calculator
Pregnancy Calculator

Quick Tips

  • •Always confirm results with your healthcare provider for the most accurate dating.
  • •An early ultrasound (6-9 weeks) provides the most reliable estimate of gestational age and conception timing.
  • •If your cycles are irregular, the last menstrual period method will be less accurate — use the due date method instead.