BABYGO® Due Date Calculator
Find out your due date and pregnancy timeline.
Select a method and provide the relevant dates to receive your estimated due date.
Select MethodNot sure? Leave it at 28 days.
Your Results
Your Due Date (EDD) Your estimated due date. Most babies arrive between 37–42 weeks.
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Example dates
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Your key dates
Useful for planning work and maternity leave.
Appointment timeline
Estimated dates. Your midwife will confirm exact times.
How we calculate your due date
Every method works out the same thing: the date you reach 40 weeks of pregnancy.
Last period
From your last period
First day + 280 daysPregnancy is counted from the first day of your last period, so 40 weeks is 280 days.
If your cycle isn't 28 days, we move the date by the difference. A 30-day cycle adds 2 days.
Conception / IUI
From conception
Conception + 266 daysConception usually happens about two weeks after your period starts, so we add 266 days instead of 280.
Use this if you know the exact date, for example from IUI or ovulation tracking.
Ultrasound
From a scan
Scan date + days left to 40 weeksYour sonographer measures your baby and tells you how far along you are. We count forward from there.
A dating scan at 11 to 14 weeks is the most accurate, so it replaces a date based on your period.
IVF
From your transfer
Day 5: +261 · Day 3: +263We know exactly how old the embryo was, so we count from the transfer date and allow for its age.
A day 5 blastocyst is two days further along than a day 3 embryo.
What is the EWC?
EWC stands for expected week of childbirth: the Sunday to Saturday week your due date falls in. Employers use it, not your exact due date, to work out maternity leave and pay.
In the UK you can start maternity leave from 11 weeks before your EWC, and you need to tell your employer by the 15th week before.
Your expected week of childbirth
This calculator gives an estimate and isn't medical advice. Speak to your midwife or GP about your pregnancy.
Due date calculator FAQs
How accurate is a due date?
It’s an estimate. Most babies arrive between 37 and 42 weeks. First-trimester ultrasound is the most accurate way to date a pregnancy.
Why is my due date different after a scan?
Ultrasound measures the baby directly (crown–rump length early on), which is more reliable than counting from your period. Clinicians typically use scan dates when there’s a significant difference.
What if I have irregular cycles?
Use the ultrasound or conception/IUI method if possible. If using LMP, the calculator adjusts for your average cycle length, but an early scan is best for accuracy.
When can I start maternity leave in the UK?
You can usually start from 11 weeks before your Expected Week of Childbirth (EWC). Your employer may have additional policies—check your contract.
How many weeks is a pregnancy?
A full‑term pregnancy is around 40 weeks. Babies are considered full term between 37–42 weeks.
Does IVF change how due dates are calculated?
Yes. IVF due dates use the embryo age at transfer: day‑3 + 263 days or day‑5 + 261 days. This accounts for development before transfer.
Can my due date change after an ultrasound?
Yes. If the scan date differs significantly from LMP dating, clinicians usually use the scan because it measures the baby directly.
What if my periods are irregular?
Use the ultrasound or conception/IUI method if possible. If using LMP, set your average cycle length—the calculator adjusts the EDD accordingly.
Pregnancy
We've put all your pregnancy essentials in one place so you don't need to do the thinking.
