Fundal Height Calculator

About the Fundal Height Calculator

Fundal height is the measurement from the pubic bone to the top of the uterus. Providers often use it between about 20 and 36 weeks as a quick office check on whether growth seems roughly in line with gestational age.

A common rule of thumb is that the number of centimeters should be close to the number of weeks pregnant, usually within about 2 cm. This calculator compares your measurement with that expected range so you can interpret what a chart note or office comment means.

It is a screening measure, not a diagnosis. A result outside the usual range may simply lead to a closer look with ultrasound, date review, or repeat measurement.

When This Page Helps

Fundal height measurement is a quick, non-invasive way to screen for growth abnormalities between ultrasound appointments. A measurement that is too small may indicate intrauterine growth restriction, while one that is too large may suggest macrosomia, polyhydramnios, or incorrect dating. Understanding your measurement empowers you to have informed conversations with your provider.

How to Use the Inputs

1. Enter your current gestational age in weeks (between 20 and 36).
2. Enter your fundal height measurement in centimeters (as measured by your provider).
3. The calculator shows the expected range and whether your measurement falls within normal limits.
4. If outside the expected range, discuss with your provider at your next visit.

Example Calculation

Tips & Best Practices

• Fundal height is most reliable between 20 and 36 weeks — before 20, the uterus is below the navel.
• After 36 weeks, the baby may drop into the pelvis, making fundal height less predictable.
• Maternal BMI, fetal position, and bladder fullness can affect the measurement.
• Your provider should measure at each prenatal visit from 20 weeks onward.
• A consistent trend is more important than any single measurement.
• Twins and multiples will measure larger than singleton pregnancies.

The Role of Fundal Height in Prenatal Care

Fundal height measurement has been a cornerstone of prenatal care for decades. It provides a quick screen between ultrasound appointments and helps providers track growth trends. Serial measurements plotted on a chart reveal whether the baby is growing consistently.

Limitations of Fundal Height

Several factors can affect measurement accuracy: maternal BMI (higher BMI may lead to larger measurements), fetal position (breech babies may measure differently), multiple gestation, and fibroids. After 36 weeks, engagement of the fetal head in the pelvis can reduce the measurement.

When Ultrasound Is Needed

If two consecutive fundal height measurements fall outside the expected range, your provider will typically order an ultrasound to assess fetal weight, amniotic fluid levels, and placental function. This step ensures that any growth concerns are identified and managed promptly.

Frequently Asked Questions

• What is fundal height?

  Fundal height (also called symphysis-fundal height or SFH) is the distance from the top of your pubic bone to the top of your uterus. It is measured in centimeters using a tape measure during prenatal visits.

• Why does fundal height equal gestational age?

  Between 20-36 weeks, the uterus grows at a remarkably consistent rate of about 1 cm per week. This correlation makes fundal height a convenient screening tool for fetal growth.

• What if my measurement is too small?

  A measurement more than 2 cm below expected may indicate slow fetal growth (IUGR), low amniotic fluid, or incorrect dating. Your provider may order an ultrasound to investigate. One small measurement alone is rarely cause for alarm.

• What if my measurement is too large?

  A measurement more than 2 cm above expected may suggest a large baby (macrosomia), excess amniotic fluid (polyhydramnios), twins, or uterine fibroids. An ultrasound can help determine the cause.

• How is fundal height measured?

  You lie on your back with an empty bladder. Your provider places a tape measure at the top of the pubic bone and extends it to the top of the uterus (fundus). The measurement is recorded in centimeters.

• Can I measure fundal height at home?

  While you can attempt it, clinical measurement is more accurate because providers are trained to identify the fundal landmark. At-home measurement can give a rough estimate but should not replace prenatal visits.