Pregnancy & family calculator
Pregnancy Due Date Calculator
Estimate your baby's due date using the first day of your last period, a conception date, an IVF embryo transfer, or an ultrasound report. Results are estimates and should be discussed with your healthcare professional.
Calculate your estimated due date
Choose the method that best matches the information you have.
Calculate fromYour dates are calculated in this browser. This tool does not send or save the dates you enter.
Your estimate
Estimated due date
This is a calendar calculation toward 40 weeks, not a measurement of fetal growth or development.
This result is an estimate, not a medical confirmation. Follow the due date established by your healthcare professional.
How does a due date calculator work?
A pregnancy due date calculator estimates the date when a pregnancy reaches 40 weeks of gestational age. The conventional calculation places the estimated due date 280 days after the first day of the last menstrual period (LMP). This convention assumes a 28-day cycle with ovulation around day 14, so an irregular cycle or an uncertain period date can affect the estimate.
When a conception or fertilization date is known, a common estimate is 266 days after that date. IVF dating uses the embryo's age and transfer date. Ultrasound dating uses the gestational age documented on the scan report. These approaches use different starting points but express the estimate on a pregnancy timeline.
How to use each method
- Last period (LMP): Enter the first day of your last period and your typical cycle length. The cycle adjustment is an estimate, especially when cycles vary.
- Conception date: Enter a known estimated conception or fertilization date. The date of intercourse alone does not confirm when conception occurred.
- IVF transfer: Enter the embryo transfer date shown by your fertility clinic and select the embryo age at transfer. Do not substitute the egg retrieval date.
- Ultrasound: Enter the scan date and the gestational age in weeks and days written on the report. This calculator does not interpret ultrasound images.
Which method should I choose?
Choose the method that matches your available records. If pregnancy resulted from IVF, use the dating provided by your fertility clinic. If your dates are uncertain, your cycles are irregular, or a scan has established a due date, ask your healthcare professional which date should guide your care. Do not average different estimates yourself.
How accurate is a pregnancy due date calculator?
A calendar-based calculator cannot predict the actual day a baby will be born. A due date is an estimate, and only a small proportion of babies arrive on that exact date. According to the American College of Obstetricians and Gynecologists (ACOG), ultrasound measurement in the first trimester is the most accurate ultrasound method for establishing or confirming gestational age. Accuracy varies with the timing and quality of the examination, and your clinician may assess the full clinical record.
Cycle-length adjustments can make an LMP-based estimate more suitable for some people, but they do not replace clinical pregnancy dating. Use the calculator for general information and preparation, not to make medical decisions.
Frequently asked questions
1. How is my pregnancy due date calculated?
The traditional method adds 280 days (40 weeks) to the first day of the last menstrual period. Conception-based, IVF, and ultrasound methods calculate from different starting information. A healthcare professional may confirm or revise the date based on your history and scan findings.
2. Can I calculate my due date without knowing my last period?
Yes, this calculator also accepts a known estimated conception date, IVF embryo transfer information, or the gestational age documented on an ultrasound report. If none of these is available or you are unsure of the dates, ask a healthcare professional about pregnancy dating.
3. Can I use this calculator for irregular menstrual cycles?
You can enter your average cycle length in the LMP method, but a cycle-length adjustment is only an estimate. Irregular ovulation can make period-based dating less reliable, so discuss an appropriate due date with your healthcare professional.
4. How is an IVF due date calculated?
IVF dating uses the embryo transfer date and embryo age. This calculator adds 263 days for a day-3 transfer, 261 days for a day-5 transfer, and 260 days for a day-6 transfer. Your fertility clinic's documented date should take precedence, particularly if its protocol differs.
5. Can an ultrasound change my due date?
It can. A healthcare professional may use ultrasound measurements, particularly during the first trimester, to confirm or revise an estimate. The decision depends on scan timing, the difference between dates, and the reliability of menstrual or assisted-reproduction dating.
6. Is my estimated due date the exact date my baby will be born?
No. It is an estimated milestone, not a promise of the birth date. Babies may arrive before or after it. Use the estimate for general planning and follow your maternity team's advice about your individual pregnancy.
7. What if my estimated due date has already passed?
This tool can show how many calendar days have passed since the estimate, but it cannot assess your or your baby's health. Contact your maternity care team for advice about monitoring and next steps; do not use this calculator to decide when to seek care.
8. Is this calculator a substitute for prenatal care?
No. It provides educational estimates only and cannot confirm a pregnancy, assess fetal growth, or replace prenatal appointments. Consult a qualified healthcare professional for pregnancy dating, screening, and care.
Trusted pregnancy dating resources
For medical guidance, consult your healthcare professional and refer to these resources: