Pregnancy Due Date Calculator
Estimate your due date from last menstrual period (LMP), conception date, or IVF transfer date. Includes current week, trimester, and major milestone dates.
How to Use
- Pick the method that matches your situation: last menstrual period (most common), conception date, or IVF transfer (Day 3 or Day 5).
- Enter the relevant date.
- For LMP method, optionally adjust your cycle length (default 28 days).
- Read the estimated due date (EDD), current pregnancy week, and trimester.
- See key milestone dates: end of trimester 1, anatomy scan, viability week, full term.
- Use this for general planning; your healthcare provider will give you the official due date.
Notes
Frequently Asked Questions
How is the due date calculated?
<strong>From LMP (Naegele's rule):</strong> first day of last menstrual period + 280 days (40 weeks). Assumes a 28-day cycle with ovulation on day 14. <strong>From conception:</strong> conception date + 266 days (38 weeks). <strong>From IVF transfer:</strong> Day-3 transfer + 263 days, Day-5 transfer + 261 days. The convention is that pregnancy is counted from LMP, even though actual gestation from conception is about 2 weeks shorter.
How accurate is the estimated due date?
Roughly: only about 4–5% of babies are born on their EDD. About 50% are born within a week before or after; about 80% within two weeks. Full term is technically 37–42 weeks. Earlier ultrasound dating (especially first-trimester) is more accurate than LMP-based dating because it doesn't depend on cycle regularity.
What if my cycle isn't 28 days?
Adjust the cycle length input. Naegele's rule assumes 28 days with ovulation on day 14. If your cycle is 32 days, ovulation is closer to day 18, and the calculation shifts the due date 4 days later. Significantly irregular cycles make LMP-based dating unreliable; ultrasound dating is much more accurate.
What are the trimesters?
<strong>First trimester:</strong> weeks 1–13 (LMP). Highest risk of miscarriage; major organ formation. <strong>Second trimester:</strong> weeks 14–27. Often the most comfortable; anatomy ultrasound around week 20. <strong>Third trimester:</strong> weeks 28–40+. Rapid fetal growth; preparation for delivery. Definitions vary slightly between sources but the 13/27 week boundaries are standard.
When is "viability"?
Around 24 weeks LMP — the point where survival outside the womb becomes possible with intensive medical care. Survival rates and outcomes improve substantially each week beyond 24. Full-term delivery is 37+ weeks; deliveries before 37 weeks are preterm. Late-preterm (34–36 weeks) generally has good outcomes.
How accurate are IVF dates?
Very — IVF transfer dates are precise to the day, so the resulting EDD is more accurate than LMP-based dating. The calculator subtracts the appropriate number of days based on whether the transfer was Day 3 or Day 5 (the day of embryo development at transfer). This precision is one of the few medical advantages of IVF cycles.
Common Use Cases
Confirming or estimating EDD
Get a quick due date when you've just learned about a pregnancy or want to verify what your provider told you.
Planning maternity leave
Use the EDD to schedule the start of leave, work-from-home arrangements, or coverage for your role.
Tracking weekly milestones
Know what week you're in to follow week-by-week pregnancy guides and apps.
Coordinating prenatal appointments
Major scans (anatomy at 20 weeks, glucose screening at 24–28) are scheduled relative to gestational age.
Surrogacy and adoption planning
Intended parents and surrogates use the same date math to coordinate logistics.
Trying to conceive
If pregnancy is suspected but unconfirmed, the calculator gives a tentative due date based on a likely conception window.
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