Due Date Calculator – Calculate Your Estimated Due Date

By Kelly Zantey
BellyBelly Creator, Mum & Birth Attendant

Wondering when your baby might be due? Only around 3-5% of babies are born on their estimated due date and around 40% are born after the estimated due date.

Dates based on your last menstrual period are most accurate, because ultrasound has a margin of error even at early stages, and is based on mathematical averages. Your body offers a more reliable estimate.

If you are given two due dates, it’s a great idea to take the one which is furthest away, because you’ll have less pressure for an induction and your baby can be born when he/she is ready, rather than anyone else. You’ll notice by making slight adjustments to your cycle length and luteal phase in the calculator below, it can effect the due date by days – because most of our bodies don’t run to the averages which standard calculators or charts use, as well as your doctor’s. Given that many women don’t know their cycle length and luteal phase, you can begin to see why it’s called an estimated due date!

Trust Your Baby…

The vast majority of babies know when it’s time to be born based on their own physical and developmental readiness, so for this reason we encourage you to remember that a pregnancy still classed as full term up to 42 weeks of pregnancy. Rest assured if you do go post-dates (as frustrating as it may be!), in a healthy pregnancy, you are giving your baby the best chance to be born happy and healthy and of course, less interventions for you too. Routine inductions only add to possible complications (including caesareans) and traumatic births.

Give your healthy, unborn baby a most precious gift of allowing him or her to decide their own birthday.

Kelly Zantey is the Creator of BellyBelly and is a mum to two beautiful children, both born before their estimated due date, in their own time. She is also a Birth Attendant; you can read about BellyBelly Birth Support here.

First Day of Last Menstrual Period (LMP):
Cycle Length:
Defaults to an average of 28 days; please adjust if required.
Luteal Cycle:
Defaults to an average of 14 days; please adjust if required.

Article Summary

Due date calculator with adjustable cycle length and luteal phase. Our advanced due date calculator will give you an estimated due date for your pregnancy. 3-5% of babies are born on their estimated due date and around 40% are born after this date.

More Pregnancy Articles