Pregnancy Due Date Calculator
Estimate your baby’s arrival date, see how many weeks pregnant you may be, and explore key pregnancy milestones. Choose the dating method that matches the information you know.
🗓️ Your pregnancy dates
This adjusts the estimate for cycles longer or shorter than 28 days.
Your dates are calculated in this page. This tool does not diagnose pregnancy or replace prenatal care.
Your estimated due date
Pregnancy milestones at a glance
Pregnancy is usually dated over about 40 weeks from the first day of the last menstrual period. Meanwhile, these milestones offer a simple overview of the timeline; your clinician may use ultrasound and your health history to refine your dates.
First trimester: early development and initial prenatal appointments commonly take place during this stage.
Second trimester: many people have a mid-pregnancy ultrasound during this period, depending on their care plan.
Third trimester: appointments often focus on growth, birth planning, and monitoring your wellbeing.
How this pregnancy due date calculator works
📅 Last menstrual period (LMP)
For a typical 28-day cycle, the calculator adds 280 days (40 weeks) to the first day of your last period. It then adjusts by the difference between your cycle length and 28 days.
💗 Conception date
If you know an estimated conception date, the calculator adds 266 days (38 weeks). Conception dates can be uncertain, so the result is still an estimate.
⏳ Gestational age
Gestational age is counted from the first day of the last menstrual period, not from conception. As a result, it is often about two weeks greater than the time since conception, although timing varies.
🩺 Why dates may change
Cycle irregularity, uncertain dates, fertility treatment, and ultrasound findings can affect pregnancy dating. Your prenatal clinician can advise which estimate is most appropriate.
Frequently asked questions
How accurate is a pregnancy due date calculator?
A calculator gives an estimate rather than an exact birth date. In addition, the result depends on how reliable your dates are and whether your cycle follows the assumed pattern. An ultrasound in early pregnancy may help your clinician confirm or revise the estimate.
How is my due date calculated from my last period?
Typically, 280 days (40 weeks) are counted from the first day of your last menstrual period. For cycles that are not 28 days long, this calculator adjusts the estimate by the difference in cycle length. However, this adjustment may not be reliable for irregular cycles.
Can I calculate my due date from conception?
Yes. If you have a reasonably reliable conception date, this calculator adds 266 days, or 38 weeks. Nevertheless, the exact date of conception can be difficult to know, so discuss your dating with your healthcare professional.
How many weeks pregnant am I?
Pregnancy weeks are commonly counted from the first day of your last period. After you enter that date, the calculator estimates completed weeks and additional days as of today. If you use conception mode, it estimates gestational age by adding approximately two weeks to the time since conception.
What if my menstrual cycle is irregular?
If your cycle length varies significantly, the last-period method may be less precise. Therefore, avoid treating the cycle adjustment as definitive and ask your clinician about dating based on your history and ultrasound findings.
Is my due date the day my baby will be born?
Not necessarily. A due date is a useful planning estimate, and many babies are born before or after it. Your care team can explain what to expect as your pregnancy progresses and when to contact them.
Can I use this calculator to confirm pregnancy?
No. This tool estimates dates only; it cannot confirm pregnancy or assess whether a pregnancy is progressing normally. Use an appropriate pregnancy test and contact a healthcare professional for personal advice.
Trusted pregnancy dating resources
For additional information, review guidance from established health organizations: