Gestational Age From Conception Calculator
Actual conception-based calendar age and explicit obstetric offset, not LMPdating or verification of conception/pregnancy. Caller independently establishes actual date/convention.
Description
Time since conception and obstetric gestational age use different date anchors.
Time since conception and obstetric gestational age use different date anchors.1
An explicitly supplied obstetric offset determines how this tool relates those coordinates.
When to use Gestational Age From Conception 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 Gestational Age From Conception Calculator and understand its results
- Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
- Enter independentlyEstablishedConceptionDate, asOfDate, callerVerifiedObstetricOffsetDays, using the field meanings and rules below, then run the tool.
- Read result.conditionalPostConceptionDays, result.conditionalObstetricGestationalDays. 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 |
|---|---|---|---|
| independentlyEstablishedConceptionDate | Independently established conception date | string | Required |
| asOfDate | As of date | string | Required |
| callerVerifiedObstetricOffsetDays | Caller verified obstetric offset days | number | Required |
Parse real Gregorian conception and as-of dates; require elapsed days 0–450 and supplied obstetric offset integer 0–28. Return post-conception days and days+offset as obstetric gestational days. The latter may exceed 450 because the bound applies before adding the offset.
postConceptionDays=ordinal(asOf)−ordinal(conception); obstetricDays=postConceptionDays+offsetDays 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.conditionalPostConceptionDays | Conditional Post Conception Days | number |
| result.conditionalObstetricGestationalDays | Conditional Obstetric Gestational Days | number |
{
"input": {
"independentlyEstablishedConceptionDate": "2026-01-01",
"asOfDate": "2026-02-01",
"callerVerifiedObstetricOffsetDays": 14
},
"output": {
"result": {
"conditionalPostConceptionDays": 31,
"conditionalObstetricGestationalDays": 45
}
}
}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 Gestational Age From LMP Calculator: Gestational age from the last menstrual period counts elapsed calendar days from the recorded menstrual anchor. For a complementary comparison, use Due Date Naegele Calculator: A cycle-adjusted Naegele calculation shifts a recorded menstrual date by a conventional duration.
References
Similar or alternative tools
- Gestational Age From LMP Calculator
Gestational age from the last menstrual period counts elapsed calendar days from the recorded menstrual anchor.
- Due Date Naegele Calculator
A cycle-adjusted Naegele calculation shifts a recorded menstrual date by a conventional duration.