Fundal Height Calculator
Calculate fundal height measurements to track fetal growth and estimate gestational age during pregnancy.
Measure from the pubic symphysis to the uterine fundus in centimeters and enter your gestational age to assess fetal growth pattern and identify potential concerns.
Fundal Height Calculator
Calculate fundal height measurements to track fetal growth and estimate gestational age during pregnancy.
About the Fundal Height Calculator
Fundal height measurement is a simple, non-invasive clinical tool used throughout pregnancy to monitor fetal growth. The fundal height is the distance in centimeters from the top of the pubic symphysis to the top of the uterus (fundus), measured using a tape measure along the curve of the abdomen. This measurement is typically assessed at every prenatal visit from about 20 weeks of gestation onward.
The primary rule for fundal height assessment is McDonald's rule: after 20 weeks of gestation, the fundal height in centimeters should approximately equal the gestational age in weeks, with a normal range of ±2 centimeters. For example, at 28 weeks, a fundal height between 26 and 30 cm is generally considered normal. This correlation holds reasonably well from 20 to 36 weeks, after which head engagement begins to lower the fundus somewhat.
Fundal height measurements that consistently fall below the expected range may indicate intrauterine growth restriction (IUGR), oligohydramnios (reduced amniotic fluid), fetal malposition, or inaccurate pregnancy dating. Measurements consistently above the expected range may suggest macrosomia (large baby), polyhydramnios (excess amniotic fluid), multiple gestation, or gestational diabetes. In either case, the finding prompts further evaluation, usually with ultrasound.
Serial measurements are more informative than single readings. Tracking growth rate — measured as the increase in fundal height per week — allows detection of growth deceleration, which may not be apparent from a single measurement that falls within the normal range. A normal growth rate is approximately 0.8–1.2 cm per week between 20 and 36 weeks.
Maternal factors that affect measurement accuracy include obesity (higher BMI makes the fundus more difficult to palpate), previous abdominal surgery, uterine fibroids, and variations in measurement technique. Fundal height is a screening tool, not a diagnostic test. Any abnormal finding should be followed up with ultrasound biometry, which provides more accurate fetal weight estimation and anatomy assessment.
This calculator uses McDonald's rule for assessment. It is an educational tool intended to support — not replace — standard prenatal care. Always discuss any concerns about fetal growth with your obstetrician or midwife.
Fundal height measurement examples
Click any example button below to load these prenatal scenarios.
| Measurement | Assessment | Clinical Note |
|---|---|---|
| FH 24 cm at 24 weeks gestation | Normal Growth (within ±2 cm) | Fundal height matches gestational age — growth tracking within expected range |
| FH 20 cm at 24 weeks gestation | Small for Gestational Age (−4 cm) | Fundal height 4 cm below expected — ultrasound recommended to assess for IUGR |
| FH 28 cm at 24 weeks gestation | Large for Gestational Age (+4 cm) | Fundal height 4 cm above expected — evaluate for polyhydramnios or macrosomia |
| FH 32 cm at 30 weeks, prev 28 cm at 26 weeks | Normal Growth (1.0 cm/week) | Serial measurements showing consistent growth of 4 cm over 4 weeks — normal velocity |
How to use the fundal height calculator
- Measure fundal height in centimeters from the pubic symphysis to the uterine fundus using a tape measure.
- Enter the fundal height measurement and current gestational age in weeks into the calculator fields.
- Optionally enter your maternal height for context and a previous measurement for growth rate calculation.
- Click Calculate to see whether your measurement falls within the normal ±2 cm range for your gestational age.
- If your result shows small or large for gestational age, discuss it with your midwife or obstetrician promptly.
Fundal height calculator FAQ
What is fundal height and how is it measured?
Fundal height is the distance in centimeters from the top of the pubic symphysis bone to the highest point of the uterus (the fundus). It is measured by placing the zero end of a tape measure at the pubic bone and running it over the curved abdomen to the fundus. The measurement is performed at each prenatal visit from about 20 weeks onward.
What is McDonald's rule?
McDonald's rule states that between 20 and 36 weeks of pregnancy, the fundal height in centimeters should approximately equal the gestational age in weeks. The clinically accepted normal range is within ±2 centimeters of the gestational age. For example, at 28 weeks gestation, a fundal height of 26–30 cm is considered normal.
What does it mean if my fundal height is small for gestational age?
A fundal height more than 2 cm below the gestational age may indicate intrauterine growth restriction (IUGR), oligohydramnios, inaccurate pregnancy dating, or fetal malposition. It does not necessarily mean something is wrong — measurement variation and maternal body habitus can affect accuracy — but it usually prompts an ultrasound to assess fetal growth and amniotic fluid volume.
What does it mean if my fundal height is large for gestational age?
A fundal height more than 2 cm above the gestational age may suggest fetal macrosomia (large baby), polyhydramnios (excess amniotic fluid), multiple gestation, or gestational diabetes. An ultrasound is typically ordered to measure estimated fetal weight and amniotic fluid index when fundal height is consistently elevated.
How accurate is fundal height measurement?
Fundal height has moderate accuracy as a screening tool, with sensitivity of about 50–70% for detecting small-for-gestational-age babies. It is less accurate in obese patients, those with fibroids, or when fetal lie is abnormal. Serial measurements by the same provider improve reliability. Ultrasound biometry provides a much more accurate assessment of fetal size.
Can I measure fundal height at home?
While it is possible to approximate fundal height at home with a measuring tape, the measurement is most accurate when performed by a trained healthcare provider using consistent technique. Self-measured values can serve as a general guide between appointments, but should not replace professional assessment. Always report any concerns about growth or fetal movement to your healthcare provider promptly.