Due Date Calculator
Calculate your estimated due date based on your last menstrual period or conception date.
Enter Your Values
Enter your values and press Calculate: you will get the result, its method, the inputs used and confidence, plus copy, print and share options.
How this calculator works
ACOG pregnancy datingv1.0.0
Due-date estimation by LMP (Naegele), conception date, IVF transfer date, or ultrasound-established EDD.
- Applies to
- Pregnancies with regular dating information
- Assumptions
- Regular cycles for LMP mode (adjustable)
- Limitations
- Ultrasound in the first trimester is the most accurate dating method
- Output
- date / gestational age
- Last reviewed
- 2026-06-01
Evidence Sources & Literature
- American College of Obstetricians and Gynecologists. Committee Opinion 700: Methods for Estimating the Due Date. Obstet Gynecol, 2017. doi:10.1097/AOG.0000000000002056.
About the Due Date Calculator
Finding out your estimated due date is one of the first exciting milestones of pregnancy. This calculator estimates your due date and shows roughly how far along you are, using the standard method based on the first day of your last menstrual period. It gives you a date to anchor the journey around, along with the gentle reminder that it is an estimate, not an appointment your baby has promised to keep.
I want to share this warmly and honestly: only about one in twenty babies actually arrives on the estimated due date. The vast majority come in the weeks around it, which is completely normal. Think of the date as the center of a window, and let your prenatal care team confirm and refine it.
How the due date is estimated
The standard method (Naegele's rule) counts 40 weeks (280 days) from the first day of your last menstrual period. Pregnancy is dated from that day rather than from conception, mostly because the last period is a date people can usually identify, while the exact moment of conception is harder to pin down. The calculator applies this method to give you an estimated due date and your current gestational age.
Why it is only an estimate
This method assumes a regular 28-day cycle with ovulation around day 14, which does not hold true for everyone. If your cycles are longer, shorter or irregular, your real timing can differ. That is why an early ultrasound is often used to confirm or adjust dating: a first-trimester scan measures the baby and can give a more precise estimate, which your provider may use instead of the period-based date.
What full term really means
A normal, healthy pregnancy can deliver any time across a range, not just on the due date. Babies born from 37 weeks are considered term, with 39 to 40 weeks regarded as full term. Arriving a week or two on either side of your estimated date is entirely typical. So rather than fixating on a single day, it helps to picture a due window of a few weeks, which takes some of the pressure off as the date approaches.
Let your provider lead
This calculator is a lovely way to get an early sense of timing and to start planning, but your prenatal care provider is the one who confirms your dates, monitors your pregnancy and guides everything from here. Use the estimate to orient yourself and enjoy the milestone, and bring any questions to your appointments, where your dating can be checked against scans and your individual situation.
Dietitian Insight: Estimated due date calculations utilize Naegele's rule adjusted for menstrual cycle length. Explore evidence-based prenatal wellness and nutrition routines, or track developmental milestones with our pregnancy gestational age calculator.
Sources & method
This calculator uses established, peer-reviewed formulas and reference ranges from recognized health and nutrition authorities. Results are estimates for general education, not a medical diagnosis. For decisions about your health, consult a qualified clinician. Reviewed by Macro & Meals Editorial Team, Content editor.
Frequently Asked Questions
How is my due date calculated?
The standard method counts 40 weeks (280 days) from the first day of your last menstrual period. Pregnancy is dated from that day rather than conception, because the last period is usually easier to identify. The calculator applies this to estimate your due date and how far along you are.
Will my baby be born on the due date?
Probably not on the exact day, only about one in twenty babies arrives on the estimated due date. The vast majority come in the weeks around it, which is completely normal. It helps to think of the date as the center of a window rather than a fixed appointment.
Why might my due date change?
The period-based method assumes a regular 28-day cycle, which does not apply to everyone. If your cycles are longer, shorter or irregular, the timing can differ. An early ultrasound measures the baby and can give a more precise estimate, which your provider may use to adjust the date.
What counts as full term?
Babies born from 37 weeks are considered term, with 39 to 40 weeks regarded as full term. Arriving a week or two on either side of your estimated date is entirely typical, so a healthy pregnancy can deliver across a range of weeks rather than on one specific day.
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