Gestational Age From FL Calculator
Interpolate independently verified actual femurLengthMillimeters to obstetric gestational days from an independently verified measurement-specific curve reference knots, strictly increasing verifiedMeasurementKnots with same-unit verifiedGestationalDayKnots. No extrapolation, universal norm or inferred biological age/individual outcome. The caller establishes cohort, measurement/calibration, applicable edition and uncertainty; illustrative knots are not authoritative reference data.
Description
Femur length can be related to gestational age through a selected biometric reference.
Femur length can be related to gestational age through a selected biometric reference.1
The supplied curve determines the result without an automatic dating correction.
When to use Gestational Age From FL Calculator
Use this tool to interpolate the supplied applicable reference knots. Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
How to use Gestational Age From FL Calculator and understand its results
- Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
- Enter callerVerifiedSource, callerVerifiedContext, callerVerifiedAsOfDate, verifiedMeasurementKnots, verifiedGestationalDayKnots, observedQueryCoordinate, using the field meanings and rules below, then run the tool.
- Read result.conditionalInterpolatedValue, result.source, result.context, result.asOfDate. 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 |
|---|---|---|---|
| callerVerifiedSource | Caller verified source; supplied assertion, not independently verified; output retention depends on the rules below | string | Required |
| callerVerifiedContext | Caller verified context; supplied assertion, not independently verified; output retention depends on the rules below | string | Required |
| callerVerifiedAsOfDate | Caller verified as of date; real Gregorian YYYY-MM-DD date for the supplied record | string | Required |
| verifiedMeasurementKnots | Verified measurement knots | list of number | Required |
| verifiedGestationalDayKnots | Verified gestational day knots | list of number | Required |
| observedQueryCoordinate | Observed query coordinate; use the exact reference token or coordinate domain stated below | number | Required |
Supply a nonblank source and context, each at most 1024 UTF-16 units, and a valid Gregorian as-of date. Enter at least two aligned finite verifiedMeasurementKnots and verifiedGestationalDayKnots values. The first list must be strictly increasing; the query must lie between its first and last knots, including endpoints. Find the enclosing pair and interpolate the second coordinate linearly, returning its supplied unit and the caller source context. This helper does not require positive values, monotone response values or percentile values in 0–100, even for percentile-named tools. Knots, units and reference suitability must be independently checked.
y(q)=y_j+(q−x_j)×(y_(j+1)−y_j)/(x_(j+1)−x_j), x=verifiedMeasurementKnots, y=verifiedGestationalDayKnots 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.conditionalInterpolatedValue | Second-coordinate value on the supplied curve at the query coordinate, in that curve's stated units | number |
| result.source | Caller source assertion copied unchanged, without independent verification | string |
| result.context | Caller applicability context copied unchanged, without independent verification | string |
| result.asOfDate | Caller reference date copied unchanged after Gregorian date validation | string |
{
"input": {
"callerVerifiedSource": "independently-reviewed-reference/edition",
"callerVerifiedContext": "femurLengthMillimeters to obstetric gestational days from an independently verified measurement-specific curve; verified cohort, protocol, units and applicability",
"callerVerifiedAsOfDate": "2026-01-01",
"verifiedMeasurementKnots": [
10,
20
],
"verifiedGestationalDayKnots": [
60,
80
],
"observedQueryCoordinate": 15
},
"output": {
"result": {
"conditionalInterpolatedValue": 70,
"source": "independently-reviewed-reference/edition",
"context": "femurLengthMillimeters to obstetric gestational days from an independently verified measurement-specific curve; verified cohort, protocol, units and applicability",
"asOfDate": "2026-01-01"
}
}
}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. Interpolation does not support extrapolation or replace a protocol-specific physical model.
Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Lists and matrices must be dense, without missing cells. Numeric lists allow at most 10000 entries; ordinary string lists allow at most 128 strings of 128 UTF-16 units each; numeric matrices allow at most 128 rows and 128 columns, subject to narrower requirements above. Extremely large composite outputs are rejected.
Alternative or Complementary methods
For a related step, use Head Circumference From GA Calculator: Head circumference is a fetal biometric measurement whose gestational relationship depends on a selected reference. For a complementary comparison, use Gestational Age From Ultrasound CRL Calculator: Crown–rump length can inform gestational dating under an applicable ultrasound reference.
References
-
Gestational Age From FL Calculator — tool.io
Similar or alternative tools
- Head Circumference From GA Calculator
Head circumference is a fetal biometric measurement whose gestational relationship depends on a selected reference.
- Gestational Age From Ultrasound CRL Calculator
Crown–rump length can inform gestational dating under an applicable ultrasound reference.