Enter your last menstrual period or conception date to find your estimated due date, current week, and key pregnancy milestones.
Due date = LMP + 280 days (Naegele's rule, standard 40-week pregnancy)
This calculator provides an estimate only. Only about 5% of babies arrive on their exact due date. Always consult your healthcare provider for personalized medical advice.
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Create Your Event ✨Note the first day of your last menstrual period. This is your starting point. If your cycles are irregular, use the conception date method instead.
Count 280 days (40 weeks) forward from your LMP. This is Naegele's rule — the global medical standard for estimating due dates since the 19th century.
An early ultrasound before 14 weeks can refine your date. If the scan differs by more than 5–7 days from LMP, your provider may adjust your due date.
Due dates are calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation around day 14. Your doctor may adjust the estimate based on early ultrasound measurements.
Only about 5% of babies arrive on their exact due date. Most are born within two weeks before or after the estimated date. A first-trimester ultrasound (before 14 weeks) provides the most accurate gestational age confirmation.
The first trimester covers weeks 1–12, the second trimester spans weeks 13–27, and the third trimester runs from week 28 until delivery around week 40.
Yes. If an early ultrasound reveals a gestational age that differs by more than 5–7 days from your LMP-based estimate, your doctor will typically update your due date to match the ultrasound measurement.
The LMP method adds 280 days to the first day of your last period. Since ovulation typically happens 14 days after LMP, if you know your conception date you subtract 14 days to get the LMP equivalent, then add 280 — the result is the same.
A doctor can estimate your due date via an early ultrasound. A scan between 6 and 10 weeks is the most accurate method when your LMP date is unknown or when irregular cycles make LMP-based calculation unreliable.