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Estimate when your baby is due from the first day of your last period, a known conception date or an IVF embryo transfer — and see how far along you are today.
Choose how you’d like to calculate. You can switch at any time.
This is an estimate, not a delivery date. In one large study, only about 5% of births happened on the estimated due date.2
Calculated from:
Your estimated due date has passedPregnancy normally lasts from 37 to 42 weeks from the first day of the last period.3 If you have any questions about your dates, your midwife or doctor can help.
This estimated due date is in the pastTo keep results simple, this calculator only shows today’s progress until 14 days after an estimated due date. This is a display setting, not a medical guideline. The term timeline below still shows how the dates were grouped.
Estimated conception dateEstimate · by conventionThe standard dating method assumes ovulation about 14 days after the first day of the last period.1 This is a conventional estimate, not the exact date conception happened — the calculator can’t determine that.
Births are grouped by how many weeks pregnant someone is. Here’s what each window means for your dates.4
This estimate is for information only. Your midwife or doctor can confirm your dates. Ultrasound measurement up to and including 13 weeks 6 days is the most accurate method to establish or confirm how far along a pregnancy is.1
Calculated at mypregnancyduedate.com/due-date-calculator
How it works
Each method counts forward from a starting date, using the pregnancy-dating conventions described in clinical guidance. The calculation happens in your browser.
By convention, the estimated due date (EDD) is 280 days — 40 weeks — after the first day of your last menstrual period.1 This convention assumes a regular 28-day cycle, so it can’t allow for irregular cycles or a later ovulation.1
LMP + 280 days
The same convention assumes ovulation around day 14 of the cycle,1 so the calculator adds 266 days to a conception date. Treat the result as an estimate: the calculator can’t confirm when conception happened.
Conception + 266 days
After IVF, the due date is set from the embryo transfer date and the embryo’s age: 261 days after a day-5 transfer, or 263 days after a day-3 transfer.1
Day 5: +261 · Day 3: +263
Pregnancy is counted from the first day of your last period, which counts as day 0, in completed weeks and days.5 So “12 weeks 3 days” means 87 days have passed since your last period began. Because the convention assumes ovulation around day 14, the count includes roughly two weeks before conception.1
Private by designEvery calculation happens in your browser. Your dates are never sent to a server, saved, or added to the page address.
What research shows
A due date is a best estimate, not an appointment. Studies show how much natural variation there is in when babies arrive.
of births happened on the estimated due date in one study of 18,708 births in Australia.2
of births in the same study happened within 7 days of the estimated due date.2
was the range of pregnancy lengths in a smaller study that measured ovulation directly, even after excluding preterm births.6
These figures describe groups of people in research studies. They aren’t a prediction for any individual pregnancy.
Your result
FAQ
Short answers, with sources. Your midwife or doctor can tell you more about your own dates.
By convention, an estimated due date is 280 days (40 weeks) after the first day of your last period.1 If you know your conception date or had IVF, the count starts from that date instead — see how this due date calculator works.
It’s a best estimate. In one study of 18,708 births, about 5% happened on the estimated due date and about two-thirds within 7 days of it.2
Yes. Choose “Conception” above and the calculator adds 266 days, following the standard dating convention.1 It’s an estimate — the calculator can’t tell you the exact date conception happened.
After IVF, the due date is based on the transfer date and the embryo’s age: 261 days after a day-5 transfer or 263 days after a day-3 transfer.1 For other embryo ages, please confirm your due date with your fertility clinic.
It can. Ultrasound measurement up to and including 13 weeks 6 days is the most accurate method to establish or confirm how far along a pregnancy is.1 If ultrasound dating differs from period-based dating by more than a set number of days, the due date is changed to match the ultrasound.1 Once your due date has been set, later changes should be rare.1
Sources last checked 3 October 2026