Educational tool only. Always confirm dates and pregnancy care plans with your obstetric provider.
What is an EDD in pregnancy?
EDD stands for Estimated Due Date. It is the date your care team expects your baby to arrive, based on information such as your last menstrual period, conception date, or IVF transfer date. Most people will not deliver exactly on their EDD, but it is still an essential reference point for prenatal visits, screening tests, and planning the final weeks of pregnancy.
How this EDD calculator works
This calculator uses standard obstetric date formulas:
- LMP method: Due date is approximately 280 days (40 weeks) from the first day of the last period, with cycle-length adjustment.
- Conception method: Due date is approximately 266 days (38 weeks) after conception.
- IVF method: Due date is calculated from transfer date plus embryo-age-adjusted days.
After calculation, you also get your current gestational age, trimester, and whether you are before, near, or past your due date.
Why cycle length matters
A 28-day cycle is often used as the default, but many cycles are naturally longer or shorter. If your cycle is usually 32 days, ovulation may happen later than day 14, and your EDD can shift forward. That is why this calculator allows a cycle-length input for the LMP method.
How accurate is a due date?
An EDD is an estimate, not a guarantee. Even with precise dating, only a small percentage of births happen on the exact date. Term pregnancy is typically considered a range, and normal delivery can occur before or after the estimated day.
Dating ultrasound often refines the estimate
In early pregnancy, ultrasound measurements are commonly used to confirm or adjust gestational age. If ultrasound and menstrual dates differ enough, your clinician may update your official due date. Always follow the date documented in your prenatal record.
Pregnancy milestones tied to EDD
- First trimester: Week 1 to 13+6
- Second trimester: Week 14 to 27+6
- Third trimester: Week 28 to birth
- Early term: 37 to 38+6 weeks
- Full term: 39 to 40+6 weeks
Knowing your due date helps schedule tests (such as anatomy scan and glucose screening), monitor growth, and discuss birth preferences.
Tips for using an EDD calculator in pregnancy
- Use the most reliable date source you have (LMP, ovulation, or IVF transfer).
- Enter dates carefully to avoid month/day mistakes.
- Use cycle adjustment only if your cycles are consistently longer or shorter.
- Update your planning based on your provider’s confirmed due date.
Important medical note
This calculator is for education and planning only. It does not diagnose conditions, confirm viability, or replace prenatal care. If you have pain, bleeding, uncertain dates, irregular cycles, or prior pregnancy complications, contact a qualified clinician promptly.