Due Date Calculator
Estimate your pregnancy due date from your last menstrual period or conception date, then see gestational age and milestone timing.
Last updated: 2026-03-18
Due date calculator
Enter your values
Estimate a pregnancy due date from your last menstrual period or conception date, then see gestational age and the next milestone.
Estimated due date
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Enter a reference date to estimate the due date, gestational age, and key pregnancy timeline markers.
Calculation History(0)
Example calculations
Tap an example to prefill the calculator with sample values.
Standard 28-day cycle
LMP on January 12, 2026
A common due-date estimate where the standard Naegele-style math applies directly.
Result: Estimated due date October 19, 2026 with second trimester beginning April 20
Longer cycle adjustment
LMP on February 3, 2026 with a 30-day cycle
Shows how a slightly longer cycle pushes the estimate later than the 28-day default.
Result: Estimated due date November 12, 2026 instead of the earlier 28-day-cycle estimate
Known conception date
Conception on February 14, 2026
Useful when a conception date is better known than the last menstrual period.
Result: Estimated due date November 7, 2026 with gestational age back-calculated from conception
How the due-date estimate works
Most due date calculators use one of two approaches. LMP mode starts from the first day of your last menstrual period and assumes ovulation near the middle of the cycle. Conception mode starts from a known conception date and counts forward from there.
Both methods produce estimates, not guarantees. If you have clinical dating information from an ultrasound or guidance from your OB-GYN or midwife, that should take priority over any self-serve calculator output.
Due date FAQs
How the estimate is calculated and why the date can still move.
How accurate is a due date calculator?
A due date calculator gives a useful estimate, not an exact prediction. Most births do not happen on the estimated due date, and ultrasound dating can shift the timeline if your clinician decides the pregnancy is measuring differently than expected.
Should I use LMP or conception mode?
Use LMP if you know the first day of your last menstrual period but not the exact conception date. Use conception mode when you have a clearer conception date and want to skip the ovulation assumption built into LMP-based estimates.
Why does cycle length matter?
The standard due-date formula assumes a 28-day menstrual cycle with ovulation around day 14. If your cycle is usually longer or shorter, adjusting the cycle length shifts the estimate so the due date lines up better with your typical ovulation timing.
Why does full term start before the due date?
Pregnancies are often considered full term at 39 weeks, while the estimated due date lands at 40 weeks. That means a birth can be full term even when it happens days or weeks before the due date itself.
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