Our fundal height calculator is an excellent tool for a variety of needs:
- Fundal height estimation based on the age of the pregnancy;
- Gestational age computed from the fundal height during pregnancy; and
- Birth weight calculations based on the fundal height by week.
Stay with us and find out how to calculate fundal height and how to measure it; we'll also talk about using our fundal height percentile calculator and how to squeeze the most out of its functions. 🤰
What is fundal height?
Fundal height is a measurement of a pregnant uterus, performed to assess fetal growth and development.
We can measure the fundal height in pregnancy by using simple tailor's tape — we need to find the length between the top of the uterus and the mother's pubic symphysis. 🤰
|💡 The pubic symphysis is a joint that connects both of our pubic bones, located just above the genitalia. That's the protruding, bony part you can feel when touching the very bottom of your front torso.|
How to calculate fundal height?
Fundal height is usually measured, but we can also calculate it using the age of the pregnancy — the gestational age.
Here's the exact formula that we used in our fundal height calculator:
Median SFH = 5.1333 + (0.1058 * GA2) - (0.02312 * GA2) * ln(GA),
- Median SFH — short form of Median symphysis-fundal height, given in centimeters (cm);
- GA — stands for the gestational age in weeks and days, turned into decimals. (e.g., 1 week 1 day = 1 ⅐ weeks = 1.14 weeks); and
- ln — a short way to write the natural logarithm.
This fundal height estimation was established by the INTERGROWTH-21st project.
How to use the fundal height calculator?
All the things you'd like to know, but you're afraid to ask, step by step!
Choose the type of calculation:
a) SFH percentile — computes the median fundal height based on your gestational age and compares it to your actual measured fundal height and its percentile.
b) SFH to gestational age — computes gestational age based on a measured fundal height.
c) SFH to fetal weight — answers the question of how to calculate baby weight by fundal height.
Input all the necessary data:
- Measured SFH — the distance between fundal height and the pubic bone, measured with the tailor's tape.
- GA weeks/days — gestational age in weeks and days.
Enjoy your results 🎉
|💡 Our calculators allow you to change the unit of almost every variable, and match it to your needs! In most of the cases the calculations can be also performed both ways!|
How to calculate gestational age from fundal height?
There are two different ways to complete this task:
We may use the McDonald's rule for fundal height by week:
- At 12 weeks, the uterus' fundus is located just above the pubic bone.
- During the 22nd week of pregnancy, the fundus of the uterus can be palpated at the height of the belly button.
- At 36 weeks, the fundus reaches its highest point — the bottom part of the sternum.
- The uterus then begins to move down — the baby prepares for the delivery, its head enters the birth canal.
We may also use the formula:
GA = 6.5858 - 2.7073 * √SFH + (1.2952 * SFH),
- GA — gestational age in weeks;
- √ — symbol of a square root; and
- SFH — symphysis-fundal height given in centimeters (cm).
How to calculate baby weight by fundal height?
Fundal height during pregnancy might be an indicator for the development and wellbeing of the fetus. There are different methods that we can use for assessing the baby's weight — one of them is the fetal weight percentile (the crown-rump length might also be of use) — another helpful and popular method is measuring the fundal height.
Here's Johnson's formula used in our fundal height — birthweight calculator:
Fetal weight = (SFH - Weight - Vertex) * 155,
|💡 This formula can be used only for babies in the vertex position (with their head down). The fetus usually takes this location after the 33-36 weeks of the pregnancy.|
- Fetal weight — given in grams (g).
- SFH — symphysis-fundal height given in centimeters (cm).
- Takes the value of 1, if mother weights >91 kg (200 lb).
- Takes the value of 0, if mother weight ≤91 kg (200 lb).
- Vertex — the top of the head of your baby.
- Takes the value of 12, if vertex is above ischial spine.
- Takes the value of 11, if vertex is below ischial spine.
Yay, you got it! Would you like to discover something more? 👶 We prepared some great tools that may help you deal with the pregnancy and your child's upbringing!
Fundal height measurement charts
We can use two different types of charts that describe the fundal height in pregnancy; the first one of them can be used by everyone, the second is mostly meant for medical professionals:
The simplest fundal height measurement chart. 🍼
Gestational age Fundal height estimation 12-14 weeks Pubic bone (top) 20-22 weeks Belly button 36-40 weeks Sternum (bottom) 37-40 weeks Uterus lowers its position
The complex version used in the fundal height percentile calculator.
The fundal height chart, 16-42 weeks of the pregnancy — all fundal heights are given in millimeters (mm).
|Gestational age (exact weeks)||Centiles|
How do I calculate fundal height?
To calculate the median symphysis fundal height (SFH) use the formula:
Median SFH (cm) = 5.1333 + (0.1058 * GA2) - (0.02312 * GA2) * ln(GA),
GA is the gestational age in weeks.
Can fundal height predict birth weight?
Fundal height can predict the birth weight of your baby — however, this method can only be used after 33-36 weeks of the pregnancy, when your baby is in the vertex position (with their head down).
In order to calculate the estimated birth weight using the fundal height we need to use the Johnson's formula:
Fetal weight = (SFH - Weight - Vertex) * 155
When to start measuring fundal height?
You may start measuring your fundal height during the 12-14th week of the pregnancy — that's when the fundus of the uterus starts to be easily palpable above your pubic bone.