Estimate a pregnancy due date from your last menstrual period, an estimated conception date, information from an ultrasound report, an IVF transfer date, or a due date already provided by your care team. A calculated date is a planning estimate; your doctor or midwife should establish and confirm the date used for care.
Pregnancy Due Date Calculator
Estimate your due date and see how far along you are. Choose the method that fits your situation.
Estimated dating milestones
Estimated dates only. This calculator does not confirm pregnancy, identify conception or assess fetal development. Use the due date confirmed by your doctor or midwife for care.
Choose the information you actually know
| Method | What to enter |
|---|---|
| Last menstrual period (LMP) | The first day of your last period and your usual cycle length in days, counted from the start of one period to the start of the next. |
| Conception date | An estimated fertilization date. A date of intercourse is not necessarily the date of conception. |
| Ultrasound scan | The scan date and the gestational age, in completed weeks plus days, recorded by your clinician. The tool does not interpret an ultrasound image. |
| IVF transfer | The transfer date and the embryo age confirmed by your fertility clinic. The menu offers day-3, day-5 and day-6 embryos. |
| I already know my due date | The estimated due date given by your care team. |
Select the method, enter its requested information and choose Calculate. Check that the date and method are correct before reading the result. If you are unsure of your last period or have irregular cycles, ask your doctor or midwife about appropriate dating instead of guessing precise inputs. The NHS explains LMP dating and the role of the dating scan.
The date arithmetic
For the LMP method, the calculator uses EDD = first day of LMP + 280 days + (cycle length − 28 days). A 28-day cycle therefore gives a date 40 weeks after LMP. The cycle adjustment is a simplifying estimate, not a measurement of when ovulation occurred.
With an LMP of March 15, 2026, a 28-day cycle gives December 20, 2026; a 35-day cycle shifts the estimate to December 27, 2026. These examples add an exact number of calendar days. Adding calendar months instead can give a different answer because months have different lengths.
The conception method adds 266 days. Ultrasound mode adds the days remaining to 40 weeks from the gestational age entered for the scan date. IVF mode adds 266 − embryo age in days to the transfer date. For a day-5 embryo transferred on May 1, 2026, that is 261 days, giving January 17, 2027. ACOG’s dating guidance describes using embryo age and transfer date for IVF pregnancies.
Gestational age is a dating convention
Pregnancy weeks are generally counted on a gestational-age scale starting about two weeks before fertilization in the standard 28-day-cycle model. Being described as six weeks pregnant therefore does not mean conception definitely happened six weeks earlier. Estimates inferred from a due date do not establish an actual conception date.
The displayed gestational-age and milestone estimates use a single reference point 280 days before the selected estimated due date. If the LMP cycle-length adjustment changes the due date, these secondary estimates change with it. That reference point is a calculation convention, not a newly discovered period or conception date.
A due date is the 40-week reference point for a particular dating estimate. First-trimester ultrasound can help establish or confirm gestational age; the clinical interpretation also depends on the reliability of the dates and how the pregnancy began. ACOG explains that early ultrasound is the most accurate method for establishing or confirming gestational age. A website cannot perform that assessment or decide whether your clinical due date should change.
A due date is not a promised birth date
The estimate helps organize care and explain pregnancy timing. It does not predict the day labor will begin, confirm pregnancy, or measure the baby’s health or growth. Do not use a countdown or milestone to schedule or delay medical care.
ACOG distinguishes these term categories:
- Early term: 37 weeks 0 days through 38 weeks 6 days.
- Full term: 39 weeks 0 days through 40 weeks 6 days.
- Late term: 41 weeks 0 days through 41 weeks 6 days.
- Postterm: 42 weeks 0 days and later.
These labels describe gestational age. They do not determine what care is appropriate for an individual pregnancy.
Common questions
Why does my scan give a different date?
LMP dating relies on recalled dates and a cycle assumption; ultrasound uses measurements interpreted by a clinician. Give both sets of information to your care team. Use the due date they establish for appointments and decisions.
Does changing cycle length make the estimate exact?
No. Cycle length does not reveal the precise day of ovulation, and cycles can vary. The adjustment changes a mathematical estimate; it does not confirm fetal age.
Can this tell me when I conceived?
No. A reverse calculation from a due date cannot establish a precise conception date or paternity. IVF records or a date entered by the user should be interpreted with the relevant clinician.
What should I do after getting a result?
Arrange or continue prenatal care and confirm the dating information with your doctor or midwife. If you have a symptom or urgent concern, seek medical advice rather than relying on this calculator. This guide provides general education and has not undergone independent clinical review.
For more on the assumptions, read how a due date is calculated.