Sprint 7 Health Hub
Pregnancy Due Date Calculator
Estimated due date from last menstrual period.
Estimated Due Date
1970-10-08
How it works
Your due date (estimated date of delivery, or EDD) is calculated as 40 weeks (280 days) from the first day of your last menstrual period (LMP) — a convention based on the assumption of a 28-day cycle with ovulation on day 14. The Pregnancy Due Date Calculator computes your EDD from multiple starting points and shows your current gestational week.
Calculation methods: - **From last menstrual period (LMP)**: EDD = LMP + 280 days. Most common method. Assumes 28-day cycle; for cycles longer or shorter than 28 days, the cycle-adjusted method is more accurate. - **From conception date**: EDD = conception date + 266 days (38 weeks from fertilisation). More precise if the conception date is known (e.g., from IVF). - **From ultrasound date**: enter the gestational age confirmed by ultrasound and the scan date. First-trimester ultrasound (before 14 weeks) is the most accurate method — accurate to within 5–7 days. - **Cycle length adjusted**: if your cycle is consistently longer than 28 days (e.g., 35 days), add the difference in days to the standard EDD calculation.
What the calculator shows: - Estimated due date in calendar format - Current gestational week and day - Trimester you are currently in - Key milestone dates: end of first trimester (13 weeks), anatomy scan window (18–22 weeks), viability milestone (24 weeks), full term (39 weeks)
Important: only approximately 4% of babies are born on their exact due date. Full term is 39–40 weeks; births from 37–42 weeks are within the normal range. Consult your healthcare provider for clinical dating.
Privacy: all calculations run in the browser. No health data is transmitted.
Frequently Asked Questions
- LMP-based dating assumes a 28-day cycle with ovulation on day 14 — accurate for people with regular 28-day cycles but increasingly inaccurate as cycle length deviates from 28 days. For cycles of 35 days, the standard LMP calculation overestimates gestational age by about 7 days. First-trimester ultrasound (before 14 weeks) is significantly more accurate — it measures the embryo directly and is accurate to ±5–7 days. For people with irregular cycles or known cycle variations, ultrasound dating supersedes LMP dating.
- Only about 4–5% of babies are born on their exact estimated due date. About 50% of births occur within a week before or after the due date. The normal range for spontaneous labour is 37–42 weeks gestational age — a 5-week window. Babies born before 37 weeks are considered preterm; those born after 42 weeks are post-term. Due dates are statistical estimates based on population averages, not predictions of when your specific baby will arrive.
- Gestational age (GA) is counted from the first day of the last menstrual period — this is the standard clinical measure used by all healthcare providers. Fetal age (embryonic age) is counted from fertilisation/conception — approximately 2 weeks less than gestational age for a typical 28-day cycle. When your doctor says '12 weeks', they mean 12 weeks gestational age (10 weeks since conception). All due date calculators, growth charts, and developmental milestones use gestational age.
- Yes, but with reduced accuracy compared to early ultrasound. If you know the date of your last menstrual period, use the LMP method. If you don't know your LMP but know approximately when you conceived, use the conception date method. The most accurate approach after a positive test is to schedule a first-trimester ultrasound at 8–12 weeks — ultrasound measurements of crown-rump length at this stage are accurate to within 5 days and will override any calculated estimate your healthcare provider uses.