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Pregnancy Due Date Calculator
Estimate a due date from the last period, conception or IVF transfer — plus the current week and milestones.
Estimated due date
| Milestone | Week | Date |
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How it’s worked out: a due date is 280 days (40 weeks) after the first day of the last period, adjusted if your cycle is longer or shorter than 28 days — or 266 days after conception. Only about 1 in 25 babies arrive on the due date itself; most come within two weeks either side. An early ultrasound gives the most accurate date, so follow your midwife or doctor’s dates if they differ. Everything here stays on your device.
About the Pregnancy Due Date Calculator
The Pregnancy Due Date Calculator estimates your baby’s due date from the first day of your last period (adjusted for cycle length), the conception date or an IVF embryo transfer. It shows how many weeks along you are, your trimester, the days to go and the dates of key milestones through your pregnancy.
How to use the Pregnancy Due Date Calculator
- Choose to calculate from your last period, conception or IVF transfer.
- Enter the date, and your average cycle length if using your last period.
- Read your estimated due date, current week and trimester.
- Check the milestone dates.
Frequently asked questions
How is a due date calculated?
Naegele’s rule adds 280 days (40 weeks) to the first day of your last period, adjusted for cycles longer or shorter than 28 days.
How accurate is a due date?
Only about 4% of babies arrive on their due date; most are born within two weeks either side. An early ultrasound gives the most accurate estimate.
How many weeks is full term?
A pregnancy is considered full term from 39 weeks to 40 weeks and 6 days, with 37–38 weeks called early term.