Pregnancy Conception Calculator – Quick, Accurate, and Free

Use this simple online tool to estimate the date you most likely conceived, based on the due date you enter.
All you need to do is:

1. Enter your due date – Use the calendar picker to select the date in the format YYYY‑MM‑DD.
2. Click “calculate” – The calculator subtracts 38 weeks (266 days) from the due date, which is the typical length of human gestation from conception to birth.
3. View the result – The estimated conception date appears in the read‑only field. Click the field to copy the date to your clipboard, or tap the X button to share it instantly on X (formerly Twitter).

What the calculator does

• Due date: The expected date of birth, usually 40 weeks after the first day of your last menstrual period.
• Conception date: The day the embryo fertilizes the egg. The calculator approximates this by subtracting 38 weeks from the due date, giving you a date in the YYYY‑MM‑DD format.

Why 38 weeks? Human pregnancy lasts about 266 days from conception to birth. Subtracting 38 weeks from the due date provides a close estimate of when conception occurred.

Use cases

• Family planning – Quickly see when conception likely happened to help schedule prenatal appointments or coordinate with a partner.
• Early pregnancy tracking – Understand how many weeks have passed since conception, useful for medical records and discussions with healthcare providers.
• Educational purposes – Illustrate the relationship between due dates and conception dates in biology or health classes.
• Personal curiosity – Wondering when that “little miracle” started? This calculator gives you an instant answer.

General information

• Accuracy: The result is an estimate; actual conception can vary by a few days.
• Privacy: No personal data is stored or sent to servers; the calculation happens entirely in your browser.
• Accessibility: Free to use, no sign‑up required, and works on all modern browsers and devices.
• Sharing: Share your result on X with a single click for quick communication with friends, partners, or healthcare professionals.

Tool summary

• conception calculator
• pregnancy calculator
• due date calculator
• estimate conception date
• pregnancy planning
• family planning tools
• free conception date tool

Use this page whenever you need a quick, reliable estimate of your conception date based on your due date. Congratulations on your pregnancy, happy free calculating!