Due Date Calculator
Calculate your due date based on last menstrual period, conception date, or IVF transfer date
Pregnancy Due Date Calculation Results
| Key Date | Date Range |
|---|---|
| First Day of Last Menstrual Period | |
| Estimated Conception Date | |
| First Trimester Ends | |
| Second Trimester Ends | |
| Estimated Due Date |
Note: This calculator provides an estimate of your due date based on the information provided. Only about 5% of women deliver their babies on their precisely estimated due date. Most babies are born within two weeks before or after.
What is a Due Date?
A Due Date (EDD) is the estimated date of delivery, which is the date by which a pregnant woman is expected to give birth. It’s an estimate, not a promise — only 4 percent to 5 percent of babies are born right on their due date. For most women, babies are born within two weeks of either side of their due date, and a full-term pregnancy is considered to be anywhere between 37 and 42 weeks.
How to Calculate a Due Date?
1. Last Menstrual Period (LMP) Method
The most common method for estimating your condition is through the date of your last menstrual period (LMP). The basic formula, or Naegele’s rule, goes like this:
- Take the date of the first day of your last period. Add 7 either way.
- Count 9 months ahead (or subtract 3 months and add 1 year and 7 days)
- This provides you with an estimated due date, which is marked at about 280 days (40 weeks) from the LMP.
Example:
If your most recent period began on Jan 1:
- Add 7 days: January 8
- Add 9 months: October 8
- Your due date is October 8.
2. Conception Date Method
If you know your conception date (or date of LMP), add 266 days (38 weeks).
3. IVF Transfer Date
For pregnancies conceived via IVF:
- Day 3 ET: 263 -Days to ET Day 3 ET: 263 +Days to ET
- Day 5 ET: Add 261 days to the ET date.
4. Ultrasound Dating
If you don’t know your LMP or your cycles are irregular, and it is over 12 weeks, an early ultrasound (if possible around 6-12 weeks) will give a better idea of the estimated due date by measurement of the fetus.
5. Pregnancy Wheels & Calculators
Physicians may also employ a pregnancy wheel or an online calculator that uses the LMP or conception date to estimate the due date.
More About Due Dates
What’s the significance of the due date?
- The due date can help towards planning for prenatal care, scheduling of tests, and getting ready for delivery. But it’s a ballpark — most babies come within a week or two weeks of the estimated due date.
What if the due date changes?
- The due date may also be manually revised according to ultrasound dating (if it is substantially different from the LMP dating value).
What if the baby is overdue or early?
- Babies who are born before 37 weeks are considered preterm.
- Full-term is 37 to 42 weeks.
- Babies born after 42 weeks are late or post-term or post-date, and labor induction may be considered to prevent complications.
Accuracy
- A small fraction of babies are born on the predicted due date. Among first-time mothers, half give birth by 40 weeks and 5 days; the halfway marker for mothers who have given birth at least once is 40 weeks and 3 days.
References
- [Johns Hopkins Medicine: Calculating a Due Date]
- [Wikipedia: Estimated date of delivery]
- [Sanford Health: What does your due date mean?]
Summary:
A due date is imprecise and is one of the many factors that put carrying a baby to term at risk, so whatever the due date, it is generally accepted to be accurate only within two or so weeks. A due date is an estimate of when a baby will be born, generally calculated based on 40 weeks from the first day of the last menstrual period. Other techniques of estimating gestation are to utilize the date of conception, IVF transfer, or ultrasound measurements. Only a tiny percentage of little ones arrive on their intended date, so it’s more of a helpful guide than a guarantee.