Gestational Age Calculator
Gestational age is how far along a pregnancy is, counted in weeks and days from the first day of the last period. Enter that date to see the weeks, the trimester and the estimated due date.
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Result
- Completed weeks
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- Trimester
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- Estimated due date
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How gestational age is counted
It is the number of weeks and days since the first day of the last menstrual period (LMP) — written like "24 weeks and 3 days", or 24+3. Because it starts from the LMP rather than conception, gestational age is about two weeks ahead of the actual age of the embryo. A full-term pregnancy is 37 to 42 weeks.
Trimesters
Pregnancy is split into three trimesters: the first through 13 weeks, the second from 14 to 27 weeks, and the third from 28 weeks until birth. Each brings different milestones and prenatal checks. The calculator shows which one today's date falls in.
LMP vs ultrasound dating
The LMP method assumes a regular 28-day cycle with ovulation on day 14. If your cycle differs, the gestational age can be off by days. An early dating ultrasound measures the embryo directly and is the more accurate reference your provider will rely on.
Informational and educational result. Not a substitute for professional advice.
Frequently asked questions
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Convert your week of pregnancy into months, following the prenatal convention where 40 weeks equals 9 months, and see which trimester it falls in.
CalculatePregnancy & BabyConception Date
Estimate when conception likely happened, from your last period or your due date. See the most likely date and the window around it.
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