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Last menstrual period · Ultrasound 기준 · Weekly fetal development informationPregnancy Week Calculator
Check the exact gestational age, days, and weekly fetal development information based on the last menstrual period start date or ultrasound reference date.
📆 Exact gestational age👶 Fetal development📊 Quarterly Division🔬 Ultrasound Standards
📝 Enter pregnancy information
Calculation criteria
Last period start date
💡 If you have gestational age measured by ultrasound, the ultrasound standard is more accurate.
📊 Calculation result
📆
After entering the date
Calculate gestational agePlease press .
Current gestational age
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Total days of pregnancy—
Pregnancy quarter—
due date—
Up to childbirth—
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Pregnancy Week Calculation Method
The gestational age is calculated from the first day of the last menstrual period. It starts at week 0, day 0, and increases by one week every 7 days. The full term (normal delivery period) is 37 to 42 weeks.
Major Milestones in Fetal Development by Week
- 4 weeks: Implantation complete, heart formation begins
- 8 weeks: Major organ formation, size approximately 1.6 cm (blueberry)
- 12 weeks: End of 1st quarter, finger formation, size approx. 5.4cm (Lime)
- 20 weeks: Fetal movement started, size approximately 16.4cm (banana)
- 28 weeks: Start of 3rd quarter, size approx. 37.6cm (branch)
- 37 weeks: Entering full term prematurely
- 40 weeks: Full-term, due date, size approx. 50cm
💡 Full term standard: Delivery between 37 and 42 weeks is within the normal range. If you experience symptoms of premature labor (regular uterine contractions, bloody show, rupture of water) before 37 weeks, please visit the hospital immediately.
Frequently Asked Questions
How do I calculate the gestational age?
Divide the number of days from the first day of your last period to today by 7 to get the week number. Example: 70 days elapsed → 10 weeks 0 days. The first day of your last period is the reference point, not the date of conception.
Can the gestational age determined by ultrasound differ from the gestational age based on menstruation?
Yes, it can vary. Differences occur if your menstrual cycle is irregular or your ovulation date differs from the average. Obstetricians and gynecologists adjust the gestational age based on ultrasound measurements.
Is giving birth before 37 weeks considered premature?
Yes, delivery before 37 weeks is classified as premature birth. Full term is 37 to 42 weeks, and after 42 weeks is a post-term pregnancy. If you experience symptoms of premature labor before 37 weeks, please visit a hospital immediately.
How big is the fetus at each gestational age?
It grows to about 1.6 cm at 8 weeks (blueberry), about 5.4 cm at 12 weeks (lime), about 16.4 cm at 20 weeks (banana), about 37.6 cm at 28 weeks (eggplant), and around 50 cm at 40 weeks. You can check fetal information by week in this calculator.