Skip to content

Pregnancy Conception Calculator

Find your conception date and fertile window for pregnancy planning.

Use LMP or due date to calculate conception timing.

Average is 28 days. Count from first day of LMP to day before next period starts.

Most Likely Conception Date

Fertile Window

Estimated Due Date

Illustration of a fertile window showing the timing of conception and ovulation.

Conception Timing Explained

Conception occurs when sperm meets egg. Sperm can survive up to 5 days in the female reproductive tract, while the egg survives about 1 day after ovulation. This creates a 6-day fertile window.

Factors That Affect Conception Timing

  • Cycle length variations affect ovulation day
  • Sperm survival (up to 5 days)
  • Egg viability (about 24 hours)
  • Ovulation timing (typically cycle day 14 in 28-day cycles)

Related Tools

Pregnancy Calculator

Full pregnancy timeline.

Due Date Calculator

Calculate delivery date.

Frequently asked questions

How do I calculate conception date?

Conception typically occurs 14 days after LMP (ovulation). Subtract 14 days from due date to get approximate conception date.

What is conception window?

Sperm survives up to 5 days, egg survives 1 day. Conception window spans about 6 days before ovulation to 1 day after ovulation.

How accurate is conception calculator?

Conception date estimate is within 1-2 days if cycles are regular. Irregular cycles reduce accuracy.

When did I conceive based on due date?

Subtract 266 days (38 weeks) from due date. This assumes full-term pregnancy and typical ovulation timing.

What is the fertility window?

The 6-day period ending on the day of ovulation. Highest chance of conception is 1-2 days before ovulation.