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Pregnancy Due Date Calculator

Calculate your estimated due date, current week of pregnancy, and key milestone dates.

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Enter the relevant date based on your selected method

Only used for LMP method — default is 28 days

How to Use This Calculator

This calculator uses three methods to estimate your due date. Choose whichever applies to your situation, enter the relevant date, and get your estimated due date plus key pregnancy milestones in seconds.

Step-by-Step

1. Choose your calculation method:

  • Last Menstrual Period (LMP) — the most widely used method; enter the first day of your last period. Doctors use this as the default because most people know this date.
  • Conception Date — use this if you tracked ovulation or used ovulation predictor kits and are confident of the date conception occurred.
  • IVF Transfer Date — for day-5 (blastocyst) embryo transfers. The calculator applies the correct 261-day adjustment automatically.
    • 2. Enter your date using the date picker. 3. Adjust cycle length (LMP method only) — if your average cycle is longer or shorter than 28 days, enter your actual cycle length. A 35-day cycle, for example, shifts ovulation — and therefore your due date — about a week later. 4. Click Calculate to see your estimated due date and all key milestones.

    What You Get

  • Estimated Due Date (EDD) — your 40-week target date
  • Current pregnancy week — exactly how far along you are today
  • Days until due — countdown to your EDD
  • Trimester start dates — when you enter the second and third trimesters
  • Viability milestone — 24 weeks, when survival outside the womb becomes possible with medical support
  • Full term date — 39 weeks, when the baby is considered fully developed

    • How the Calculation Works

    The LMP method applies Naegele's Rule: add 280 days (40 weeks) to the first day of your last period, then adjust for cycle length. This is the same formula your OB or midwife uses. The conception and IVF methods count forward from the known date using the standard gestational windows (266 and 261 days respectively).

    A Note on Accuracy

    Due dates are estimates. Only about 5% of babies arrive on their exact EDD. Most are born within a two-week window on either side. An early ultrasound (ideally before 14 weeks) is the gold standard for confirming gestational age and may revise your EDD slightly.

    Formula

    Naegele's Rule: Due Date = LMP + 280 days (adjusted for cycle length)

    Frequently Asked Questions

    How accurate is an estimated due date?

    Only about 5% of babies are born on their exact due date. Most are born within 2 weeks either side. Early ultrasound (before 14 weeks) gives the most accurate estimate and may revise the date calculated from your LMP.

    What is full term?

    Full term is 39–40 weeks. "Early term" is 37–38 weeks, and "late term" is 41–42 weeks. Babies born at 37 weeks are considered viable but may have more feeding and breathing challenges than those born at 39+ weeks.

    What if my cycle is not 28 days?

    This calculator adjusts for non-standard cycles. If your cycle is 35 days, ovulation typically occurs around day 21 rather than day 14, shifting your due date about 7 days later. Enter your average cycle length for a more accurate result.

    When is the first trimester over?

    The first trimester ends at 13 weeks and 6 days. The second trimester runs from week 14 to 27. The third trimester is week 28 until birth. Miscarriage risk drops significantly after week 12.

    How is an IVF due date calculated differently?

    For a day-5 (blastocyst) IVF transfer, the due date is 261 days after the transfer date. For a day-3 transfer, it is 263 days. This is because the embryo is already 5 days old at transfer, so the total gestational window is shorter than the 266 days used for natural conception.

    What happens if my due date changes after an ultrasound?

    It is common for an ultrasound to revise your EDD by a few days to a couple of weeks, especially if your cycle is irregular. The ultrasound-adjusted date becomes your official EDD. This does not mean anything is wrong — it simply reflects the actual size and development of the baby.

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