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Pregnancy Due Date Calculators
Simple, calm tools for the dates that matter in pregnancy: your estimated due date, how many weeks pregnant you are, and an estimated conception date. Everything is calculated in your browser, and every medical statement links to its source.
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Each one takes a single date and gives a clear, labelled estimate.
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Due Date Calculator
Estimate your due date from your last period, a known conception date or an IVF transfer date.
Open CalculatorPregnancy Weeks Calculator
See how far along you are today, in weeks and days, from your last period or your due date.
Open CalculatorConception Date Calculator
Get a conventional estimate of when conception occurred, from your due date or last period.
OpenHow dating works
How is a pregnancy due date estimated?
Pregnancy is dated from the first day of the last menstrual period, not from conception.1 By convention, the estimated due date is 280 days after that day.2 The convention assumes a regular 28-day cycle with ovulation on day 14, so it is a starting point rather than a prediction.2
Ultrasound measurement up to and including 13 weeks 6 days is the most accurate method to establish or confirm how far along a pregnancy is.2 If your midwife or doctor has given you a due date, use theirs.
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Medical statements are numbered and link to published guidance or peer-reviewed research.
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Results are labelled as estimates, with the convention behind them explained.
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Sources
- International Statistical Classification of Diseases and Related Health Problems, 10th Revision. Volume 2: Instruction manual. Sixth Edition, 2019. World Health Organization (WHO). 2019. icd.who.int
- Methods for Estimating the Due Date. Committee Opinion No. 700. American College of Obstetricians and Gynecologists (ACOG), Committee on Obstetric Practice; American Institute of Ultrasound in Medicine; Society for Maternal-Fetal Medicine. Obstet Gynecol 2017;129:e150-4. Reaffirmed 2025. acog.org
Sources last checked 3 October 2026