Fundal Height Calculator
Estimate gestational age from a fundal height measurement taken at a prenatal checkup, using the widely used McDonald rule.
What fundal height measures
Fundal height is the distance in centimeters from the top of the pubic bone to the top of the uterus (the fundus). During routine prenatal visits between roughly 20 and 36 weeks, this measurement is used as a quick, low-cost check on how a pregnancy is progressing.
How this calculator works
This tool applies McDonald rule, a long-standing obstetric formula that estimates gestational age in weeks as fundal height in centimeters multiplied by 8 and divided by 7. In practice, from about 20 to 36 weeks, fundal height in centimeters is often close to the number of weeks pregnant, give or take a couple of centimeters, which is why the calculator also shows a typical range.
Fundal height varies with factors such as fetal position, amniotic fluid level, maternal body size, and the number of babies carried, so a reading outside the typical range is common and not automatically a cause for concern. This calculator is for general educational and planning purposes only and does not replace assessment by a qualified healthcare provider.