Due Date Calculator
Calculate your estimated due date, current pregnancy week, trimester, and key milestones.
Due Date Calculator
Estimate your baby's arrival date
How to Use
- 1 Select a calculation method: Last Period (LMP), Conception Date, or IVF Transfer Date
- 2 For LMP method, enter the first day of your last menstrual period and your average cycle length
- 3 For Conception method, enter the date you believe conception occurred
- 4 For IVF method, enter the embryo transfer date and select Day-3 or Day-5 embryo type
- 5 View your estimated due date, current pregnancy week, trimester, and key milestones instantly
What You Get
Three calculation methods for estimating your pregnancy due date: Last Menstrual Period (Naegele's rule with cycle length adjustment), known conception date, and IVF embryo transfer date (Day-3 or Day-5). Shows current gestational age, trimester, safe delivery window (37–42 weeks), and a pregnancy milestone timeline.
Input: Last period: January 1, 2025, cycle: 28 days
Output: Due date: October 8, 2025. Currently 6 weeks, 2 days. First trimester.
Input: Conception date: January 15, 2025
Output: Due date: October 8, 2025. LMP estimated: January 1, 2025.
Input: IVF Day-5 transfer: January 20, 2025
Output: Due date: October 8, 2025. Conception estimated: January 15, 2025.
How is my due date calculated?
The most common method uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, the calculator adjusts by adding or subtracting the difference from 28 days. From a known conception date, the calculator adds 266 days (38 weeks).
How accurate is a due date calculator?
Due date calculators provide an estimate. Only about 4–5% of babies are born on their exact due date. Most babies arrive within a two-week window around the estimated date. First-trimester ultrasounds (before 13 weeks) are the most accurate dating method, typically accurate to within 5–7 days. This calculator gives you a reliable starting point, but your healthcare provider may adjust based on ultrasound measurements.
Can my due date change?
Yes. Your healthcare provider may adjust your due date after an ultrasound scan, especially if there is a discrepancy of more than one week between the ultrasound dating and LMP dating. Early ultrasounds (8–13 weeks) are most accurate for dating. Irregular cycles, uncertain LMP dates, or IVF conception are common reasons for adjustments.
What is Naegele's rule?
Naegele's rule is the standard formula used to calculate an estimated due date. The rule states: take the first day of the last menstrual period (LMP), add one year, subtract three months, and add seven days. This is equivalent to adding 280 days to the LMP date. The rule assumes a regular 28-day menstrual cycle with ovulation occurring on day 14.
How many weeks is a full-term pregnancy?
A full-term pregnancy is 39 to 40 weeks. Early term is 37–38 weeks, full term is 39–40 weeks, late term is 41 weeks, and post-term is 42 weeks or later. The safe delivery window is generally considered 37–42 weeks. Babies born before 37 weeks are considered preterm and may need additional medical care.
What if my cycle is longer or shorter than 28 days?
If your cycle is regularly longer or shorter than 28 days, the LMP calculation adjusts for this. With a longer cycle (e.g., 35 days), ovulation occurs later, so the due date shifts forward by the difference (7 days later). With a shorter cycle (e.g., 24 days), ovulation occurs earlier, shifting the due date backward by 4 days. Enter your average cycle length for a more accurate estimate.
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