Pregnancy Calendar Generator

Most due dates are calculated as being "40 weeks from your last period" but it would be more accurate to say it's 38 weeks after you ovulate.

If you know when you ovulate, we'll use that date.

Otherwise, we count 14 days back from your next period (found with your average cycle length) to find the day you probably ovulated. If you know this phase (the luteal phase) isn't 14 days, then you can determine your ovulation date and use that instead.

Please note that your doctor will probably use the traditional calculation. If so, you can match due dates by putting the first day of your last period and picking a cycle length of 28 days.

And if you already have a due date and would like to work backwards, we can now do that too!

I am simply an enthusiast (of pregnancy and of coding answers to my own questions, like what's the earliest I could conceive and still be in a wedding next summer) and this generator is meant for entertainment purposes only.

Method 1: If you know when you ovulate

Date of last ovulation:


Method 2: Use your average cycle

Date of first day of last period:

Average cycle length:

Method 3: Work back from a due date

Your Due Date:


Optional: Add special dates to your calendar

If you want to mark any special dates on your calendar, enter them and a short description here
You can add these after the fact and click "Generate or refresh"

Date (YYYY/MM/DD)    Description


Mark the 37th week onwards
(Some airlines only allow flying until the end of week 36)


First trimester
Second trimester
Third trimester
Special day
Due date
Date past 36 weeks (if checkbox selected)
Date outside of 42 weeks
The week number indicates how many weeks you are on the bolded day
(e.g. you are two weeks pregnant on the 8th)
This should bring it in line with common usage

Hover over the text on a special day to see your description of the day
I am defining trimesters as weeks 0-11, 12-27, and 28-40, inclusive.


Printing Tips

If you want to print your calendar, be sure to use Print Preview and only choose the pages you need. I should have successfully programmed in page breaks where they are useful.
You will probably need to change a setting in Page Setup to "Print Background (Colors and images)" or something similar.