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Current gestational age
Estimate a pregnancy due date and current week from the last period or conception.
This tool estimates a pregnancy due date and the current gestational week, calculated from either the first day of the last menstrual period (LMP) or an estimated conception date. It also indicates which trimester the pregnancy is currently in and how many days remain until the estimated due date.
The most common clinical method, known as Naegele's rule, estimates a due date as 280 days (40 weeks) from the first day of the last menstrual period, based on an average 28-day cycle with ovulation around day 14. If you're calculating from an estimated conception date instead, this tool adds roughly 14 days to shift it to an equivalent LMP-based reference point, then applies the same 280-day estimate. This is the same general approach used by most standard pregnancy wheels and calculators.
Only a small percentage of babies are actually born exactly on their calculated due date — most arrive within a window of a couple of weeks either side. Cycle length varies between individuals, ovulation doesn't always occur on day 14, and a range of clinical factors can shift the actual delivery date. This calculator provides the same standard estimate used as a planning reference point, but it is not a substitute for dates confirmed by a healthcare provider, particularly ultrasound-based dating, which is generally more precise than LMP-based calculation alone.
Gestational age is conventionally counted from the first day of the last menstrual period, not from the estimated date of conception, which is why 'week 4' of pregnancy is typically only about two weeks after conception itself. Pregnancy is generally divided into three trimesters: the first spans roughly weeks 1 through 13, the second spans roughly weeks 14 through 26, and the third continues from week 27 to full term around week 40.
It uses the same standard 280-day (Naegele's rule) estimation method used widely as a planning reference, but it's an estimate only. For the most accurate due date, rely on your healthcare provider's assessment, which often incorporates ultrasound dating.
Both methods aim to reach the same estimated 40-week mark, but calculating from an assumed conception date depends on knowing that date precisely, while LMP-based calculation depends on a regular, known cycle length — small assumptions in either method can shift the result by a few days.
Gestational age is counted from the first day of your last period, not from conception, so a pregnancy that's medically '4 weeks along' typically reflects only about 2 weeks since actual conception.
Only a small minority. Full-term delivery is generally considered normal anywhere from about 3 weeks before to 2 weeks after the calculated due date.
No, always defer to your healthcare provider's dating, especially once ultrasound measurements are available, since those are typically more precise than a calculation based on LMP or estimated conception alone.