Pregnancy Due Date Calculator
Estimate your pregnancy due date using your last period, conception date, IVF transfer date, or ultrasound scan. The calculator also shows your current pregnancy week, trimester, estimated conception date, and a simple pregnancy timeline.
Calculate Pregnancy Due Date
Choose the method that matches the information you know best. Last period is common, while conception, IVF, and ultrasound can be better when those dates are known.
Pregnancy Progress
Progress is based on a 40-week pregnancy estimate.
Key Dates
Timeline Visual
What this pregnancy due date estimate means
A pregnancy due date calculator gives an estimated delivery date, often called the EDD. It is not a promise that labor will happen on that exact day. The date is mainly used to organize prenatal visits, testing windows, ultrasound timing, and pregnancy milestones.
If you know your last menstrual period, the calculator can use that. If you know a conception date, IVF transfer date, or ultrasound gestational age, those options are also included. If you want to work backward from a due date later, use CalcMora’s ovulation calculator by due date. During pregnancy, the pregnancy weight gain calculator can help estimate general weight-gain ranges by week and BMI.
How the due date is calculated
The last-period method adds 280 days to the first day of the last menstrual period. This is the classic 40-week pregnancy estimate. The conception method adds 266 days because conception usually happens about two weeks after the start of the last period in a typical 28-day cycle.
IVF dating uses the embryo transfer date and embryo age. For example, a 5-day embryo transfer means the embryo has already developed for about five days, so the calculator adds the remaining pregnancy days to estimate the due date. Ultrasound dating works by subtracting the scan gestational age from the ultrasound date to estimate an LMP-equivalent date, then adding 280 days.
How to use this calculator
1. Choose your best date source
Use last period if you remember it and have regular cycles. Use conception, IVF, or ultrasound if those details are more reliable.
2. Add cycle or scan details
For LMP, choose your average cycle length. For ultrasound, enter the scan date plus the weeks and days shown.
3. Check the timeline
Review your due date, current week, trimester, estimated conception date, and pregnancy progress visual.
4. Confirm with prenatal care
Use the result for planning, then confirm official dating with your doctor, midwife, or fertility clinic.
Which calculation method should you choose?
| Method | Best when | How it estimates the date |
|---|---|---|
| Last menstrual period | You know the first day of your last period and cycles are fairly regular. | Adds 280 days, with an optional cycle-length adjustment. |
| Conception date | You know or strongly estimate when conception happened. | Adds 266 days to the conception date. |
| IVF transfer | You had fertility treatment with a known embryo transfer date. | Uses transfer date plus embryo age to estimate the remaining pregnancy length. |
| Ultrasound | You have a scan date and gestational age from the scan report. | Back-calculates an LMP-equivalent date, then adds 280 days. |
Examples
Example 1: Last period method
If the first day of the last period was January 1 and the cycle length is 28 days, the calculator adds 280 days. It also estimates ovulation around January 15 and shows the current pregnancy week based on the date you choose as “today.”
Example 2: IVF transfer method
If a 5-day embryo transfer happened on March 10, the calculator treats the embryo as already five days developed. It adds the remaining pregnancy days to estimate the due date and shows an LMP-equivalent date for timeline planning.
Why due dates can change
A due date can change when early ultrasound measurements do not match the period-based estimate, when the last period is uncertain, or when cycles are irregular. First-trimester ultrasound is often more useful for pregnancy dating than later ultrasound because early fetal development is more consistent.
Try not to think of the due date as one exact deadline. It is better understood as the center of a wider birth window. Your care team may use the confirmed date to plan scans, screening tests, and discussions about labor. After birth, CalcMora’s baby percentile calculator can help you track growth estimates using age and measurements.
Frequently Asked Questions
What is a pregnancy due date calculator?
A pregnancy due date calculator estimates the expected delivery date using pregnancy timing information such as the first day of the last menstrual period, conception date, IVF transfer date, or ultrasound gestational age. The result is an estimate, not a guaranteed birth date. Most babies are not born exactly on their due date, but the date helps organize prenatal care, scans, tests, and pregnancy milestones.
How is a due date calculated from the last menstrual period?
The common last-period method adds 280 days, or 40 weeks, to the first day of the last menstrual period. This assumes a typical 28-day cycle with ovulation around day 14. If your cycle is longer or shorter, the calculator adjusts the estimate by the difference between your cycle length and 28 days. This still remains an estimate because ovulation can happen earlier or later.
Is conception date more accurate than last period date?
A known conception date can be useful, especially when it is based on fertility tracking or treatment records. The calculator adds about 266 days to the conception date to estimate the due date. However, many people do not know the exact conception date, and intercourse date is not always the same as fertilization date. A healthcare professional may rely more on early ultrasound dating when dates are uncertain.
Can this calculator estimate due date after IVF?
Yes. The calculator includes IVF transfer dating for 3-day and 5-day embryo transfers. IVF due-date estimates are usually based on the embryo age and transfer date. This can be more precise than a typical last-period estimate because the timing of fertilization and embryo development is known. Still, your fertility clinic or obstetrician should confirm the official pregnancy dating used for care.
Why does ultrasound dating matter?
Ultrasound dating can be especially helpful when the last period date is unknown, cycles are irregular, or the pregnancy does not match menstrual dating. First-trimester ultrasound is often the most accurate time for dating a pregnancy. This calculator can estimate a due date when you enter the ultrasound date and the gestational age shown on the scan, but your clinician’s confirmed date should guide medical care.
Does this calculator replace a doctor or midwife?
No. This tool is for educational purposes only. It does not diagnose pregnancy health, fetal growth, miscarriage risk, labor timing, or any medical condition. Due dates can be adjusted after ultrasound or clinical review. Always follow advice from your doctor, midwife, fertility clinic, or qualified healthcare professional.