Due date calculator
Your estimated due date, how far along you are and the dates to look out for.
- 100% free
- No sign-up
- Runs in your browser
How to use Due date calculator
- Choose how to count
- Enter the date
- See your dates
First day of your last period
Estimated due date
Pick a date to see your due date.
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How to use Due date calculator
Choose how to count
Use the first day of your last period, the day you conceived, or the date of an IVF embryo transfer.
Enter the date
Pick the date. For your last period, add your usual cycle length; for IVF, choose a day 3 or day 5 embryo.
See your dates
Get your due date, how many weeks and days pregnant you are today, your trimester and a list of key milestones.
Why use Utils365
Three ways to count
Last menstrual period, known conception date or IVF transfer, each worked out the way clinics do.
Adjusted for your cycle
Longer or shorter cycles than 28 days move the due date, just as midwives adjust it.
Milestones with dates
Scan windows, trimesters, full term and 42 weeks, each with its calendar date.
Private
Nothing you enter is sent or stored. It all happens in your browser.
Frequently asked questions
How is the due date calculated?
Add 280 days (40 weeks) to the first day of your last period. A last period on 1 January 2026 gives a due date of 8 October 2026. This is Naegele’s rule, counted in days so leap years come out right.
What if my cycle isn’t 28 days?
Ovulation usually comes about 14 days before the next period, so a longer cycle means later ovulation. With a 35-day cycle the due date moves 7 days later.
How do I calculate my due date from conception?
Add 266 days (38 weeks) to the conception date. Pregnancy weeks are still counted from two weeks before conception, so you’re ‘2 weeks pregnant’ on the day you conceive.
How is an IVF due date worked out?
Add 266 days to the transfer date and take off the embryo’s age: 261 days after a day 5 transfer, or 263 days after a day 3 transfer.
How many weeks pregnant am I?
Count from the first day of your last period. If it was 73 days ago you’re 10 weeks and 3 days pregnant. The calculator shows this for today.
How accurate is a due date?
Only about 4% of babies arrive on their due date. Most are born between 37 and 42 weeks. An early dating scan, usually at 11 to 14 weeks, gives the most reliable date.
When does each trimester start?
The first trimester runs to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth.