Estimate the timeline from the information you actually have
A pregnancy due date calculator estimates a 40-week obstetric timeline from a selected dating basis. This page supports the first day of the last menstrual period, known conception, ultrasound dating, IVF transfer, or an already established due date. Each method uses its own offset rather than forcing every user through an LMP-only formula.
The result shows the estimated due date, current gestational age, trimester, days completed and remaining, conception estimate, week-by-week checkpoints, and a visual position on the 40-week timeline. It is planning information, not a diagnosis or a promise about delivery day.
Choose the dating basis before entering dates
- Select LMP, conception, ultrasound, IVF transfer, or known due date based on the most reliable information available.
- Enter the requested date and, for IVF, the embryo age at transfer; use the reference date for the timeline snapshot.
- Calculate and verify the method and input date shown with the estimate.
- Discuss discrepancies, symptoms, cycle uncertainty, or a revised clinical date with a qualified maternity-care professional.
Why an estimated due date can change
LMP dating conventionally assumes a 28-day cycle with ovulation around day 14. Irregular cycles, uncertain dates, assisted reproduction, and early ultrasound findings can support a different estimate. ACOG guidance describes establishing and documenting the best obstetric estimate rather than repeatedly changing dates without clinical reason.
The calculator displays the chosen method so two estimates can be compared without forgetting why they differ.
Forty weeks is a reference timeline, not an appointment
Only a small share of births occur on the exact estimated due date. The week-12, week-20, week-28, and week-37 markers are general calendar checkpoints, not individualized care schedules. Follow local prenatal guidance and the clinician who knows the pregnancy.
When a calculator is the wrong next step
Seek clinical advice for pain, bleeding, reduced fetal movement, fluid loss, severe symptoms, concerns about dates, or any urgent change. An online estimate cannot evaluate symptoms, confirm pregnancy, assess fetal development, or replace ultrasound interpretation.
Frequently asked questions
Evidence-aware answers about dating methods, accuracy, ultrasound, IVF, and clinical limitations.
How accurate is a pregnancy due date calculator?
It estimates a reference date from the selected method. Actual delivery timing varies, and clinical dating may change when better information becomes available.
Which due-date method should I choose?
Use the best documented information: IVF details for assisted conception, clinician-provided ultrasound dating when applicable, or LMP/conception when reliable.
Can an ultrasound change the due date?
A clinician may revise dating based on ultrasound timing, measurement differences, and established professional guidance. Do not change it from this page alone.
How is an IVF transfer due date estimated?
The calculation accounts for the transfer date and embryo age so gestational dating aligns with the conventional 40-week framework.
Does the result confirm gestational age medically?
No. It is calendar arithmetic from supplied dates. Clinical records and qualified professionals determine the official obstetric estimate.
What should I do about pregnancy symptoms?
Contact an appropriate healthcare professional or emergency service. This calculator cannot assess symptoms or provide individualized medical advice.