Enter measurement details
Use the current gestational age and measured symphysis fundal height. Add the optional previous reading to estimate interval change.
Example data table
These example values show how the screening rule is commonly interpreted. They are educational examples, not diagnostic cutoffs.
| Gestational Age | Expected SFH | Usual Screening Range | Example Measured SFH | Example Interpretation |
|---|---|---|---|---|
| 24w 0d | 24.0 cm | 22.0 to 26.0 cm | 24.5 cm | Within expected screening range. |
| 28w 0d | 28.0 cm | 26.0 to 30.0 cm | 27.0 cm | Still within the usual band. |
| 32w 0d | 32.0 cm | 30.0 to 34.0 cm | 29.5 cm | Slightly smaller than dates. |
| 36w 0d | 36.0 cm | 34.0 to 38.0 cm | 38.0 cm | Upper end of the expected band. |
| 38w 0d | 38.0 cm | 36.0 to 40.0 cm | 36.0 cm | May be normal if engagement lowers the height. |
Formula used
1) Gestational age in decimal weeks
GA decimal = weeks + (days ÷ 7)
2) Expected fundal height
Expected SFH ≈ gestational age in weeks from about 20 to 36 weeks.
3) Usual screening range
Typical range = expected SFH ± 2 cm
4) Difference from expected
Difference = measured SFH − expected SFH
5) Estimated age from measurement
Estimated GA by SFH ≈ measured centimeters
6) Optional interval trend
Weekly change = (current − previous) ÷ (days between ÷ 7)
This calculator applies a practical screening rule. It does not replace prenatal assessment, imaging, or clinician judgment.
How to use this calculator
- Enter the current gestational age in completed weeks and extra days.
- Enter the current symphysis fundal height in centimeters.
- Add the previous reading and the interval in days if you want a trend estimate.
- Select any context factors that may influence the measurement.
- Press Calculate to view the expected range, discrepancy, trend, and graph.
- Download the result as CSV or PDF for records or discussion.
FAQs
1) What is symphysis fundal height?
It is the distance from the pubic symphysis to the top of the uterus, measured in centimeters. Clinicians use it as a simple screening check for growth and dating trends.
2) When is the one-centimeter-per-week rule most useful?
It is most helpful from roughly 20 to 36 weeks in a singleton pregnancy. Before 20 weeks and after 36 weeks, the relationship becomes less reliable.
3) What difference is usually considered acceptable?
A result within about 2 cm of expected is often treated as a usual screening range. Technique, bladder filling, fetal position, and body habitus can change the value.
4) Can BMI affect the reading?
Yes. Higher BMI can make abdominal landmarks harder to feel consistently. That does not make the result meaningless, but it can reduce agreement with the simple screening rule.
5) Do twins or multiples change interpretation?
Yes. Multiple pregnancies often measure differently from singleton pregnancies. The basic one-centimeter-per-week comparison is less dependable in twins or higher-order multiples.
6) Should I worry if the result is outside the range?
Not automatically. A single reading is a screening clue, not a diagnosis. Repeated differences, rapid changes, symptoms, or clinician concern deserve closer review.
7) Can I use home measurements?
You can record them, but consistency matters. Home measurements vary because landmark identification is harder without training. Use them for discussion, not diagnosis.
8) Does a lower number always mean growth restriction?
No. Engagement, breech position, fibroids, bladder status, and measurement technique can lower or raise fundal height. Clinical assessment adds the full picture.
Important note
This tool is an educational screening aid for pregnancy tracking. It is not a medical diagnosis tool and should not replace prenatal care, clinician examination, or imaging.