Due Date Calculator
Estimate a due date from a last menstrual period, a conception date or an IVF transfer, using the ACOG method.
Result
Estimated due date: October 22, 2026Estimate
A first-trimester ultrasound is a more accurate dating method than this one. About 4 in 100 babies arrive on the estimated date.
- Gestational age
- 19w 4d
- Trimester
- second
- Days remaining
- 143
- Estimated conception date
- January 29, 2026Estimate
- Dating from
- January 15, 2026Estimate
https://calcgallery.com/pregnancy/due-date-calculator/
How to use the Due Date Calculator
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- Enter that date, and your average cycle length if you are working from a period.
- Set the progress date to today to see gestational age and trimester.
- Read the due date as an estimate with a wide spread around it, not an appointment.
An ultrasound date supersedes this one
ACOG is explicit that a first-trimester ultrasound is the most accurate method of establishing a due date, and that where it disagrees with an LMP-based estimate beyond a defined margin, the scan date should be used. If you have had a dating scan, that date is the one to work from. This page is arithmetic on a calendar and is not antenatal care.
How it is calculated
From your last period. Naegele’s rule adds 280 days to the first day of the last menstrual period:
estimated due date = LMP + 280 daysThose 280 days are forty weeks, and they count from the period rather than from conception, which is why gestational age is always about two weeks ahead of the age of the embryo. The rule assumes a 28-day cycle with ovulation around day 14. For a different average cycle the calculator shifts the date by the difference, so a 35-day cycle moves it a week later.
Gestational age itself always counts from the last period and does not shift with cycle length. A longer cycle changes when you are due; it does not change how pregnant you are today.
From a conception date. 266 days, which is the same 280 less the conventional two-week offset.
From an IVF transfer. 261 days from a day-5 blastocyst transfer, or 263 from a day-3 transfer. These are the most precise of the three, because the age of the embryo is known rather than inferred.
Trimesters follow the usual convention: the first through 13 weeks and 6 days, the second from 14w0d to 27w6d, the third from 28w0d.
What the date does not mean
Only about four in a hundred babies arrive on the estimated date. A normal term spans several weeks around it, and the estimate’s job is to date the pregnancy for clinical purposes rather than to name a day.
Nothing on this page assesses whether a pregnancy is progressing normally. It counts days.
Practical tips
Set the progress date to today. The calculator has no clock of its own — deliberately, because that is what makes it give the same answer every time it runs — so the field starts at a date the site maintains.
Know your cycle length if you can. It is the single input that moves the due date, and a week either way is a meaningful difference.
A first-trimester scan is worth more than any calculation here. If one is offered, its date is the better one.
Gestational age is measured from your period, not from conception. At the moment of conception you are already counted as about two weeks pregnant, which surprises almost everyone.
Leap years are handled. The date arithmetic uses the site shared calendar helpers, so a pregnancy spanning 29 February counts correctly.
With your numbers
- As of the date entered that is 19w 4d, in the second trimester, with 143 days to go
- 280 days from the first day of your last period gives October 22, 2026
Quick reference
A first-trimester ultrasound is a more accurate dating method than this one. About 4 in 100 babies arrive on the estimated date.
| Example | Estimated due date |
|---|---|
| LMP 2026-01-15, 28-day cycle | October 22, 2026 |
| LMP 2026-01-15, 32-day cycle | October 26, 2026 |
| LMP 2026-01-15, 24-day cycle | October 18, 2026 |
| Conception 2026-01-29 | October 22, 2026 |
| Day-5 transfer 2026-02-03 | October 22, 2026 |
| Day-3 transfer 2026-02-01 | October 22, 2026 |
| LMP 2026-03-01, 28-day cycle | December 6, 2026 |
| LMP 2027-12-31, into a leap year | October 6, 2028 |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
5 sources
ACOG Committee Opinion No. 700, Methods for Estimating the Due Date, Obstet Gynecol 2017;129:e150-4 (reaffirmed 2025), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date: "By convention, the EDD is 280 days after the first day of the LMP."
Used for
- Gestational duration added to the last menstrual period.
ACOG Committee Opinion No. 700, Methods for Estimating the Due Date, Obstet Gynecol 2017;129:e150-4 (reaffirmed 2025), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date. Derived, not printed: 280 days from the LMP less ovulation on day 14 of a 28-day cycle, both as ACOG states; it agrees with ACOG's 261 days from a day-5 and 263 from a day-3 embryo transfer.
Used for
- Gestational duration counted from conception rather than the last period.
ACOG Committee Opinion No. 700, Methods for Estimating the Due Date, Obstet Gynecol 2017;129:e150-4 (reaffirmed 2025), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date: "for a day-5 embryo, the EDD would be 261 days from the embryo replacement date".
Used for
- Gestational duration counted from a day-5 blastocyst transfer.
ACOG Committee Opinion No. 700, Methods for Estimating the Due Date, Obstet Gynecol 2017;129:e150-4 (reaffirmed 2025), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date: "the EDD for a day-3 embryo would be 263 days from the embryo replacement date".
Used for
- Gestational duration counted from a day-3 embryo transfer.
ACOG Committee Opinion No. 700, Methods for Estimating the Due Date, Obstet Gynecol 2017;129:e150-4 (reaffirmed 2025), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date: the LMP method "assumes a regular menstrual cycle of 28 days, with ovulation occurring on the 14th day".
Used for
- Cycle length Naegele rule assumes. Longer or shorter cycles shift the estimate.
Common questions about the Due Date Calculator
- How accurate is a due date?
- About four babies in a hundred arrive on the estimated date. A normal term spans several weeks either side, which is why clinicians talk about a due window rather than a due day. The estimate is useful for planning and for dating the pregnancy; it is not a prediction of a particular day.
- Why does my scan say something different?
- Because a first-trimester ultrasound measures the pregnancy and this calculation infers it from a date. ACOG states that a scan in the first trimester is the most accurate dating method available, and that when it disagrees with the LMP estimate beyond a defined margin the scan date should be used. A date from a scan supersedes this one.
- What if my cycles are irregular?
- Naegele rule assumes ovulation around day 14 of a 28-day cycle. The calculator adjusts for a different average cycle length, but an irregular cycle has no reliable average to adjust by, so the estimate becomes correspondingly unreliable. That is one of the cases where ultrasound dating matters most.
- How is IVF dating different?
- It is more precise, because the age of the embryo at transfer is known exactly rather than inferred. A day-5 blastocyst transfer is dated 261 days to the estimated due date and a day-3 transfer 263 days, which removes the uncertainty about when ovulation and fertilisation happened.
- Why does the page ask for a progress date instead of using today?
- Because the calculators on this site are pure functions: given the same inputs they return the same answer, forever, with no hidden dependency on when they ran. That is what makes them testable. The field carries a default date that the site maintains, and you set it to today yourself.