Interpretation
| Result | Meaning |
|---|---|
| < 14w0d | First trimester |
| 14w0d–27w6d | Second trimester |
| ≥ 28w0d | Third trimester |
| 37w0d–41w6d | Term |
| ≥ 42w0d | Post-term |
Formula
EDD = LMP + 280 days + (cycle length − 28) days · GA (days) = (date − LMP) − (cycle length − 28)
Clinical pearls
- ACOG: first-trimester ultrasound is the most accurate dating; redate if the CRL estimate differs from LMP by >5 days before 9w0d or >7 days from 9w0d to 13w6d.
- A pregnancy without an ultrasound confirming or revising the EDD before 22w0d is considered suboptimally dated.
- Once set, the EDD should rarely be changed; later ultrasounds measure growth, not dates.
Examples
due date lmp 2026-01-01edd for LMP March 3 2026 with 32 day cycleshow far along is she, lmp 2026-02-14, today 2026-05-20
FAQ
How is a due date calculated?
Add 280 days (40 weeks) to the first day of the last menstrual period. For cycles longer or shorter than 28 days, add or subtract the difference.
How accurate is the due date?
Only about 4–5% of babies are born on the due date; most deliver between 37 and 42 weeks. Early ultrasound dating is more accurate than LMP.
What if my cycle is 35 days?
Ovulation is about 7 days later than in a 28-day cycle, so add 7 days to the standard LMP + 280 day due date.