Fundal Height Calculator

Fundal height, also called symphysis-fundal height (SFH), is the distance in centimeters from the pubic symphysis to the top of the uterus (fundus). It is routinely measured during prenatal visits from around 20 weeks onward to monitor fetal growth. As a rule of thumb, SFH in centimeters roughly equals gestational age in weeks between 20 and 36 weeks.

Lie flat on your back with knees slightly bent. A clinician uses a tape measure to find the distance from the top of the pubic bone (pubic symphysis) to the highest point of the uterus (fundus). The measurement is taken in centimeters. Always use the same method each visit to ensure consistency.

SFH provides a useful screening estimate but has limitations. It is most reliable between 20–36 weeks and can be affected by maternal BMI, fetal position, amniotic fluid levels, and fibroids. Ultrasound biometry remains the gold standard for dating and growth assessment, especially in early pregnancy.

Fundal height measurement typically begins at around 20 weeks of gestation, when the uterus reaches the level of the umbilicus. It is measured at every antenatal visit from that point until delivery, usually every 2–4 weeks.

A high SFH percentile (above the 90th centile) may suggest a large-for-gestational-age baby, excess amniotic fluid (polyhydramnios), or multiple pregnancy. A low percentile (below the 10th centile) may indicate a small-for-gestational-age baby or reduced amniotic fluid (oligohydramnios). Your healthcare provider will order an ultrasound to investigate any concerning measurements.

Fundal height provides a rough estimate of fetal weight. The commonly used Johnson's formula estimates fetal weight (in grams) based on the SFH measurement. However, ultrasound-based biometry with formulas such as Hadlock's provides a more reliable estimate of birth weight, especially later in pregnancy.

No — fundal height standards and this calculator are designed for singleton pregnancies only. In twin or higher-order multiple pregnancies, the uterus is larger than expected for gestational age, so standard SFH centile charts do not apply. Ultrasound is the appropriate tool for monitoring growth in multiple pregnancies.

This calculator uses the INTERGROWTH-21st derived median formula: Median SFH = 5.1333 + (0.1058 × GA²) − (0.02312 × GA²) × ln(GA), where GA is gestational age in weeks. Gestational age from SFH is estimated using: GA = 6.5858 − 2.7073 × √SFH + (1.2952 × SFH).