History

No history yet

Conception Calculator

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

First Day of Last Period

How it works

Conception typically occurs about 11-21 days after the first day of your last period. Or if you know your due date, we count back 266 days.

Enter dates to calculate

Understanding the Conception Calculator

Estimate the date conception likely occurred based on your due date or the first day of your last menstrual period.

Guide

How to use the Conception Calculator

1Select calculation method: 'By Last Period' or 'By Due Date'.
2Enter the required date (LMP or Due Date).
3View estimated conception date and key pregnancy milestones.

Applications

Common Use Cases

Dating Pregnancy: Estimating gestational age.

Retroactive Tracking: Understanding when conception happened.

Timeline Planning: Visualizing trimesters.

The Maths Behind the Calculation

Conception ≈ LMP + 14 days OR Due Date - 266 days

Conception typically occurs around ovulation, which is about 14 days after the start of your last period. Pregnancy is counted as 280 days (40 weeks) from LMP, meaning conception is roughly 266 days before the due date.

Knowledge Base

Frequently Asked Questions

Can I know the exact day of conception?

Unless you had intercourse only once during your fertile window or used IVF, it is difficult to know the exact day. Sperm can live for up to 5 days, so conception might happen days after intercourse.

Why is pregnancy counted from the last period?

Because the exact date of ovulation/conception is often unknown, doctors use the Last Menstrual Period (LMP) as a reliable medical start date for the pregnancy.

Regional Notice: United States

"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."

Loading Pregnancy Conception calculator...

Regional Notice: United States

"Federal tax estimates are based on 2024 brackets. Consult a tax professional for official filing."