Pregnancy Due Date Calculator
Estimate your due date from the first day of your last menstrual period or a known conception date, and see the current estimated week of pregnancy with a simple timeline.
Your Details
Health note: This gives an estimated due date for general information only. Actual delivery timing varies, and this is not a substitute for prenatal care. Please see a doctor, midwife or other qualified healthcare professional for pregnancy care and advice.
Results
Estimated due date
Estimated pregnancy week today
Estimated trimester
Estimated timeline
How this calculator works
Using the first day of your last menstrual period (LMP), the estimated due date is LMP + 280 days (Naegele's rule), shifted by the difference between your usual cycle length and 28 days. Using a conception date, it is conception + 266 days. Pregnancy weeks are counted from the LMP (or from two weeks before conception), so the current estimated week is the number of whole weeks and days since then. Trimesters are shown as weeks 0–13, 14–27 and 28 onward. All dates are calculated in your browser and not saved.
How is the estimated due date calculated?
The most common method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last menstrual period, assuming a 28-day cycle; this calculator adjusts for longer or shorter cycles. If you know the conception date, it adds 266 days (38 weeks) instead.
How accurate is an estimated due date?
It is an estimate. Only a small share of babies are born on their estimated due date, and a healthy delivery commonly happens anywhere from about 37 to 42 weeks. Your healthcare provider may adjust the date based on an early ultrasound scan.
Why is pregnancy counted from the last period?
By convention, pregnancy weeks are counted from the first day of the last menstrual period -- about two weeks before conception in a typical cycle -- because that date is usually easier to know than the date of conception.
Is my information stored?
No. The dates you enter are used only in your browser. Nothing is saved, sent to our servers or included in analytics.
Disclaimer: This calculator is for general information only and does not provide medical advice or replace prenatal care. See our Disclaimer and Terms of Use for more detail.