Hadlock 4-Parameter EFW Calculator
Named HadlockBPD/HC/AC/FL four-parameter log10gram model with all actual ultrasound dimensions in CENTIMETERS, not millimeters. Formula-specific estimated weight is not observed fetal mass, gestational age, growth percentile, viability or clinical decision; qualified measurement/formula applicability review required.
Description
The four-parameter Hadlock model estimates fetal weight from head and abdominal measurements plus femur length.
The four-parameter Hadlock model estimates fetal weight from head and abdominal measurements plus femur length.1
Centimeter input units and the specified model coefficients determine the grams estimate.
When to use Hadlock 4-Parameter EFW Calculator
Use this tool to calculate or review the supplied observations under the stated rules. Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
How to use Hadlock 4-Parameter EFW Calculator and understand its results
- Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
- Enter observedBpdCm, observedHcCm, observedAcCm, observedFlCm, using the field meanings and rules below, then run the tool.
- Read result.conditionalEstimatedFetalWeightGrams. Use the units and sign conventions below.
- Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| observedBpdCm | Observed bpd cm | number | Required |
| observedHcCm | Observed hc cm | number | Required |
| observedAcCm | Observed ac cm | number | Required |
| observedFlCm | Observed fl cm | number | Required |
Require BPD, HC, AC and FL in centimeters, each strictly positive and no greater than 100. Evaluate the exact four-parameter Hadlock base-ten model for grams. No coefficient fitting, uncertainty interval or biometric acquisition is performed.
estimatedGrams=10^(1.3596−0.00386×AC×FL+0.0064×HC+0.00061×BPD×AC+0.0424×AC+0.174×FL) Use the matching field units and the exact boundary, ordering and reference rules above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Structured result; its nested fields below contain the actual calculation or selected reference | object |
| result.conditionalEstimatedFetalWeightGrams | Conditional Estimated Fetal Weight Grams | number |
{
"input": {
"observedBpdCm": 8,
"observedHcCm": 30,
"observedAcCm": 30,
"observedFlCm": 6
},
"output": {
"result": {
"conditionalEstimatedFetalWeightGrams": 2085.4510476931687
}
}
}Limitations and assumptions
Dating evidence, acquisition conditions and applicable clinical references remain independently established. The output describes supplied observations or a conditional model without diagnosing an outcome, choosing a dose or verifying clinical applicability.
Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Extremely large composite outputs are rejected.
Alternative or Complementary methods
For a related step, use Shepard EFW Calculator: The Shepard model estimates fetal weight from biparietal diameter and abdominal circumference. For a complementary comparison, use Hadlock 3-Parameter EFW Calculator: The three-parameter Hadlock model uses head circumference, abdominal circumference and femur length.
References
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Hadlock 4-Parameter EFW Calculator — tool.io
Similar or alternative tools
- Shepard EFW Calculator
The Shepard model estimates fetal weight from biparietal diameter and abdominal circumference.
- Hadlock 3-Parameter EFW Calculator
The three-parameter Hadlock model uses head circumference, abdominal circumference and femur length.