Fundal Height
Estimate symphysis-fundal height (SFH) by gestational age using the INTERGROWTH-21st formula. Compare measured SFH against percentiles, compute gestational age, or estimate fetal weight with Johnson's formula for India, US, UK.
About This Calculator
The Fundal Height Calculator helps expectant parents and healthcare providers assess fetal growth by measuring the distance from the top of the pubic bone to the top of the uterus (symphysis-fundal height or SFH). After 20 weeks of pregnancy, this simple tape measurement in centimeters closely matches the gestational age in weeks, making it a trusted screening tool for monitoring healthy fetal development.
Our calculator offers three powerful modes. SFH Percentile mode uses the INTERGROWTH-21st formula established by the International Fetal and Newborn Growth Consortium (Papageorghiou et al., BMJ 2016) to compute the expected median SFH for your gestational age and determine your baby's growth percentile. The formula is: Median SFH = 5.1333 + (0.1058 × GA²) − (0.02312 × GA²) × ln(GA), where GA is gestational age in weeks. GA from SFH mode works in reverse — it estimates gestational age from your measured fundal height using the formula GA = 6.5858 − 2.7073 × √(SFH) + (1.2952 × SFH). Fetal Weight mode applies Johnson's formula to estimate birth weight: Fetal weight (g) = (SFH − weight factor − vertex factor) × 155, which is valid after 33-36 weeks with the baby in vertex position.
The results classify your baby's growth into three categories: SGA (Small for Gestational Age) — below the 10th percentile, indicating the baby is smaller than 90% of peers of the same age; AGA (Appropriate for Gestational Age) — between the 10th and 90th percentiles, considered normal; and LGA (Large for Gestational Age) — above the 90th percentile, larger than 90% of peers. The interactive growth chart plots your SFH measurement against the 5th, 50th, and 95th percentile reference curves from the INTERGROWTH-21st multinational study.
Fundal height measurement is a standard part of prenatal care worldwide. While it is a valuable screening tool, it has a sensitivity of approximately 50-60% for detecting abnormal growth. Always confirm significant findings with ultrasound assessment and discuss results with your healthcare provider.
Regional Notes
India: The INTERGROWTH-21st formula and SFH reference charts are recommended by FOGSI (Federation of Obstetric and Gynaecological Societies of India) and widely used across Indian hospitals. Indian-specific growth standards (such as those from the Indian Council of Medical Research) may differ slightly from multinational averages. Fundal height is measured in centimeters starting at 12-14 weeks in most Indian prenatal care protocols.
US: The American College of Obstetricians and Gynecologists (ACOG) recommends serial fundal height measurements beginning at 24 weeks as a routine component of prenatal care. ACOG Practice Bulletin No. 204 notes that SFH measurement has a detection rate of 56% for SGA and 54% for LGA. Ultrasound should be used when clinical suspicion of abnormal growth arises.
UK: The National Institute for Health and Care Excellence (NICE) recommends symphysis-fundal height measurement at each antenatal appointment from 24 weeks onwards using a tape measure. NICE guidelines state that SFH should be plotted on a customised growth chart for the most accurate assessment. The INTERGROWTH-21st reference used here provides multinational standards — discuss results with your midwife for local interpretation.
Frequently Asked Questions
What is fundal height and why is it measured during pregnancy?
Fundal height (symphysis-fundal height or SFH) is the distance in centimeters from the top of the pubic bone (pubic symphysis) to the top of the uterus (fundus). It is measured with a tape measure starting around week 12-14 of pregnancy to assess fetal growth and development. After 20 weeks, fundal height in centimeters typically corresponds closely to gestational age in weeks, making it a simple and effective screening tool for appropriate fetal growth.
How is fundal height calculated from gestational age?
Our calculator uses the INTERGROWTH-21st formula: Median SFH = 5.1333 + (0.1058 × GA²) − (0.02312 × GA²) × ln(GA), where GA is gestational age in weeks. This formula was derived from the International Fetal and Newborn Growth Consortium's large multinational study published in the BMJ (Papageorghiou et al., 2016). For example, at 20 weeks the median SFH is 19.8 cm, and at 36 weeks it is 34.9 cm.
What is the normal fundal height range by week?
Fundal height typically falls within a range around the median. At 20 weeks, the 5th to 95th percentile range is 17.3–22.2 cm (median 19.8 cm). At 30 weeks, it is 26.7–32.5 cm (median 29.6 cm). At 40 weeks, it is 34.6–41.3 cm (median 38.0 cm). Generally, SFH within 2 cm of the gestational age in weeks is considered normal after 20 weeks. A measurement significantly above or below may warrant further evaluation.
How do I measure fundal height at home?
To measure fundal height: lie flat on your back with legs straight, locate the top of your pubic bone (pubic symphysis), find the top of your uterus (fundus) by gently pressing on your abdomen, use a flexible tape measure to measure from the pubic bone to the top of the uterus. The measurement should be taken with an empty bladder for accuracy. Always confirm significant findings with your healthcare provider as home measurements can vary.
What does it mean if my fundal height is above or below expected?
A fundal height below the 10th percentile (SGA — Small for Gestational Age) may indicate intrauterine growth restriction (IUGR), oligohydramnios (low amniotic fluid), or incorrect dating. A fundal height above the 90th percentile (LGA — Large for Gestational Age) may suggest macrosomia, polyhydramnios (excess amniotic fluid), multiple pregnancy, or incorrect dating. These findings require clinical correlation with ultrasound and should be discussed with your obstetrician.
Can fundal height predict birth weight?
Yes, fundal height can estimate fetal weight using Johnson's formula after 33-36 weeks when the baby is in vertex (head-down) position: Fetal weight (grams) = (SFH − weight factor − vertex factor) × 155. The weight factor is 1 if the mother weighs over 91 kg (200 lb) and 0 otherwise. The vertex factor is 12 if the baby's head is above the ischial spine and 11 if below. This is a clinical estimation tool — actual birth weight depends on many factors.
When should fundal height measurement start and stop?
Fundal height measurement typically begins at 12-14 weeks when the uterus becomes palpable above the pubic bone. It continues through the pregnancy until around 36-38 weeks when the baby descends into the pelvis (lightening) and the fundal height may drop slightly. After 40 weeks, the measurement remains relatively stable as the uterus cannot expand further. The most clinically useful period is 20-36 weeks when SFH correlates most reliably with gestational age.
How accurate is the fundal height measurement?
Fundal height measurement accuracy depends on several factors including the examiner's technique, maternal habitus, bladder fullness, fetal position, and the quality of the tape measure. Inter-observer variability of ±1-2 cm is common. The INTERGROWTH-21st study showed that SFH is a reasonable screening tool for identifying abnormal fetal growth, but ultrasound assessment is recommended when concerns arise. Fundal height has sensitivity of approximately 50-60% for detecting SGA and LGA.