Expected Date of Birth Calculator
Use this tool to estimate your baby’s due date using one of three common methods: last menstrual period (LMP), conception date, or IVF embryo transfer date.
Today’s date:
Note: This provides an estimate and should not replace medical advice from a qualified healthcare provider.
How this expected date of birth calculator works
An expected date of birth calculator estimates your due date by applying standard obstetric timing rules. Most pregnancies are measured as 280 days (40 weeks) from the first day of the last menstrual period, not from the day of conception. That can feel confusing at first, but it is the medical convention used worldwide.
This calculator gives you a practical estimate and also shows your current gestational age, trimester, and time remaining. It is helpful for planning appointments, preparing your birth timeline, and understanding where you are in your pregnancy journey.
Three ways to estimate your due date
1) Last Menstrual Period (LMP)
This is the most common approach. We add 280 days to the first day of your last period and adjust based on cycle length when provided. If your cycle is longer or shorter than 28 days, ovulation likely happened later or earlier, and the estimate shifts accordingly.
2) Conception Date
If you know when conception occurred, we estimate the due date by adding 266 days (38 weeks). This method can be more precise when conception timing is known with confidence.
3) IVF Transfer Date
IVF pregnancies use a dedicated formula that accounts for embryo age at transfer. The calculator supports both day-3 and day-5 embryo transfers, which are standard clinical references.
Why estimated dates can change
Even with accurate formulas, your due date is still an estimate. Many pregnancies do not end exactly on that date. Your provider may adjust your expected date of birth after an early ultrasound, especially if fetal measurements differ from cycle-based estimates.
- Irregular menstrual cycles
- Uncertain LMP date
- Late ovulation or implantation
- Differences found on first-trimester ultrasound
- Multiple gestation (twins or more) with separate care plans
How to use your estimate in real life
Plan prenatal care milestones
Once you have a due date estimate, you can map prenatal visits, routine screening windows, and expected trimester transitions.
Prepare work and family logistics
A projected date helps with leave planning, childcare decisions, travel limitations, and family support scheduling.
Track progress week by week
Tracking gestational age can make medical updates easier to understand. Most providers communicate growth, tests, and recommendations by pregnancy week.
Frequently asked questions
Is the expected date of birth exact?
No. It is a strong estimate, not a guarantee. Birth can occur before or after the projected date and still be completely normal.
Which method is most accurate?
IVF transfer dates and known conception dates are often very precise. For naturally conceived pregnancies, early ultrasound is typically the best clinical confirmation.
Should I rely only on online calculators?
Use calculators for planning and education, but always confirm pregnancy timelines with your OB-GYN, midwife, or fertility specialist.
Final note
This expected date of birth calculator is designed to be simple, fast, and useful. It gives a solid starting point for your pregnancy timeline, but your healthcare team should guide final dating, medical decisions, and personalized care.