Conception Calculator

Estimate when conception occurred based on your due date or birth date.

Due date or birth date

Average cycle length (days)

This calculator estimates when conception likely occurred based on your due date. Results are approximate as exact conception timing is difficult to determine.

Most Likely Conception Date

Oct 30, 2025

Possible Conception Window

Earliest

Sat, Oct 25

Latest

Sat, Nov 1

Daily Conception Likelihood

Sat, Oct 25

Sun, Oct 26

Mon, Oct 27

14%

Tue, Oct 28

27%

Wed, Oct 29

31%

Thu, Oct 30

33%

Fri, Oct 31

Sat, Nov 1

Likelihood Distribution

Sat, Oct 25(2.5%)

Sun, Oct 26(6.7%)

Mon, Oct 27(11.7%)

Tue, Oct 28(22.5%)

Wed, Oct 29(25.8%)

Thu, Oct 30(27.5%)

Fri, Oct 31(1.7%)

Sat, Nov 1(1.7%)

These dates are estimates. Sperm can survive up to 5 days, making exact conception dates uncertain.

How Conception Date is Calculated

Conception typically occurs about 266 days before the due date, during ovulation. The fertile window spans about 6 days, with the highest chances on ovulation day and the day before.

Factors Affecting Conception

Sperm can survive in the reproductive tract for up to 5 days, while an egg survives only 12-24 hours after ovulation. This means conception can occur from intercourse that happened several days before ovulation.

Accuracy Considerations

Conception date calculations are estimates. The actual conception could have occurred anywhere within the fertile window, making it difficult to pinpoint the exact date.