Pregnancy Week Fetus Size Calculator

Pregnancy Week Fetus Size Calculator helps estimate Korea-related pregnancy, ovulation, fetal week, due-date, and maternity planning assumptions in English.

Pregnancy week and fetal size inputs

Pregnancy week result

Current gestational age

20w 1d

141 total days

Estimated due date

2026-12-29

50.4% complete

Days until due date

139 days

Current-date based, matching the Korean function

Overall growth percentile

50%

Within the expected fetal growth range.

Biparietal diameter

61 mm vs P50 61 mm

Percentile 50%, Z-score 0, status normal.

Femur length

45 mm vs P50 45 mm

Percentile 50%, Z-score 0, status normal.

Abdominal circumference

204 mm vs P50 204 mm

Percentile 50%, Z-score 0, status normal.

Estimated fetal weight

600 g vs P50 600 g

Percentile 50%, Z-score 0, status normal.

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Pregnancy week and fetal size calculator

This guide translates the Korean pregnancy week and fetal size content. The calculation uses the source WHO 2024 fetal growth chart and INTERGROWTH-21st style percentile tables for gestational week, due date, fetal measurements, percentile, and Z-score.

Week calculation

The Korean calculator can start from either LMP or due date. LMP mode counts the days from the last menstrual period to today, then divides by 7 to show weeks and days. Due-date mode back-calculates LMP as due date minus 280 days and then uses the same day count.

The due date in LMP mode is LMP plus 280 days. Percent complete is elapsed days divided by 280, capped between 0 and 100 percent. The calculator keeps the current-date behavior of the Korean function so the English result changes naturally over time.

Fetal measurements

The fetal size analysis accepts common ultrasound measurements: CRL, BPD, FL, AC, and EFW. BPD is biparietal diameter, FL is femur length, AC is abdominal circumference, and EFW is estimated fetal weight. The source tables store P3, P10, P50, P90, and P97 for each supported week.

For each measurement, the calculator interpolates a Z-score between percentile reference points and converts it to a percentile. Values below the 10th percentile are marked below range, values above the 90th percentile are marked above range, and the remaining values are normal in the model.

  • BPD, FL, and AC are measured in millimeters.
  • EFW is measured in grams.
  • Overall fetal size is the average percentile of entered measurements.
  • Below the 10th percentile is flagged as small.
  • Above the 90th percentile is flagged as large.

Reference interpretation

The Korean guide explains that fetal growth should be read as a trend, not as a single number. A one-time low percentile can reflect dating, fetal position, measurement variability, or normal constitution. Repeated low percentiles or falling trend should be discussed with the obstetric team.

A high percentile should also be interpreted with context such as parental build, dating accuracy, gestational diabetes screening, amniotic fluid, and previous growth. The calculator is designed to organize numbers before a visit, not to diagnose growth restriction or macrosomia.

Common use cases

Use the week calculator when you know LMP or due date but want a quick gestational age. Use the fetal size section after an ultrasound report provides BPD, FL, AC, and EFW. The result helps compare those numbers with the week-specific P50 reference.

If ultrasound dating and LMP dating differ, use the due-date planner together with this page. The week and fetal-size calculator is best for monitoring the current week and growth percentile after the pregnancy date has already been decided.