Work it out from

Last periodFirst day of it ConceptionDate you conceived IVF transferEmbryo transfer date UltrasoundAge at a scan Due dateAlready known

First day of your last period

Cycle length, days

A cycle is from the first day of one period to the first day of the next. 28 days is the usual figure; a longer cycle moves the date later.

How to use Conception Date Calculator

Takes about 1 minute. You need the first day of your last period, or a conception, transfer or scan date.

Choose what you knowPick Last period, Conception, IVF transfer, Ultrasound or Due date.

Type the dateChoose the date. For Last period, set your usual cycle length; for IVF, the embryo's age; for Ultrasound, the weeks and days on the report.

Read the datesThe estimated due date, how far along you are today and the dates along the way appear at once.

Type the due date you were given, or switch to Last period, and the likely conception date appears with how far along you are today. Conception usually happens about two weeks after the first day of the last period, 266 days before the due date; the exact day can differ by several days either way.

How it works

Conception Date Calculator is a web page that does its work on your own device. Everything you type or choose is worked out by your browser and never sent to a server, so nothing is stored and there is nothing to delete. There is no account, no sign-up and no limit on how often you use it.

Why the date is only approximate

Sperm can survive for several days and ovulation does not always fall on the same day of the cycle, so the day of conception can be a few days before or after the date shown. An early ultrasound dates the pregnancy more closely than any calculation from a period.

Other shortcuts

Due Date Calculator · IVF Due Date Calculator

Conception Date Calculator

Work it out from

Dates along the way