Health & Fitness Calculators
Pregnancy Conception Calculator
Estimate the conception date from a due date.
FreeNo sign-upWorks in your browser
Estimates conception ~266 days before the due date (280 days from the last period).
Estimated conception date
Sun, July 26, 2026
Last menstrual period (est.)
Sun, July 12, 2026
Estimated fertile window
Tue, July 21, 2026 – Tue, July 28, 2026
About the Pregnancy Conception Calculator
Working backward from a due date, this calculator estimates when conception likely occurred — about 266 days before the due date — along with the corresponding last-period date and fertile window. It's helpful for understanding a pregnancy's timeline or answering 'when did I conceive?'.
How to use the Pregnancy Conception Calculator
- 01Enter your estimated due date.
- 02Read the result instantly — it recalculates as you type.
- 03Adjust the numbers to model different scenarios.
Frequently asked questions
How is conception date estimated?
Roughly 266 days before the due date (or ~14 days after the last period start). It's an estimate — actual conception timing varies.
Can it be exact?
No — sperm can survive several days, so conception can happen a few days after intercourse. The result is a best estimate.