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Free Beta-hCG Subunit Unit Converter
Free β-hCG is the active component of the human Chorionic Gonadotropin hormone, produced by the placenta during pregnancy. Unlike the intact Beta-hCG (Total hCG), the free subunit is specifically included in first-trimester maternal screening tests.
Clinically, Free β-hCG is measured as a component of the **Combined Test** (alongside PAPP-A) or the **Triple/Quad Screen** to assess the risk of fetal chromosomal aneuploidies. High levels are strongly associated with **Down syndrome (Trisomy 21)**, while low levels are associated with **Edwards syndrome (Trisomy 18)**. It is also used as a tumor marker for germ cell tumors and choriocarcinoma. This converter ensures accurate switching between the common mass unit (ng/mL) and activity units (mIU/mL or IU/L).
SI / Activity Units
RecommendedMilli-International Units per milliliter or Nanomoles per liter.
Mass Units
Clinical Context
Reference Interpretation: Free Beta-hCG levels are typically reported as **Multiples of the Median (MoM)**, where 1.0 MoM represents the expected median value for that specific gestational age.
In Down syndrome screening, Free Beta-hCG MoM is usually high (median ≈ 2.0 MoM). The conversion factor between mass and activity is assay-dependent, but often simplified clinically: **1 ng/mL ≈ 1 mIU/mL**. The molar conversion factor relies on the MW of the free subunit (15 kDa ): 1 ng/mL ≈ 66.6 pmol/L.
Clinical References
How to Use This Calculator
Follow these steps to get accurate clinical conversions instantly.
Enter Values
Input your laboratory results into the corresponding unit field (e.g., ng/mL). You can use either dot or comma decimals.
Automatic Conversion
The calculator works in real-time. As you type in one field, all other units are instantly updated.
Verify Units
Check the SI Units section. Note that ng/mL is numerically identical to µg/L.
Reset
Use the Clear button to reset all fields before starting a new calculation.
Frequently Asked Questions & Tips
They are used interchangeably in screening due to close approximation, but they measure mass versus biological activity.
The free subunit is a more reliable marker for Down syndrome risk assessment than the intact Total hCG molecule during the first trimester.