Calculator
Example Data Table
| Case | Total Testosterone | Unit | SHBG | FAI Result | Comment |
|---|---|---|---|---|---|
| Example A | 18 | nmol/L | 45 | 40.00% | Inside a sample broad review range |
| Example B | 55 | ng/dL | 30 | 6.36% | Lower calculated index |
| Example C | 8 | ng/mL | 25 | 110.94% | Higher calculated index |
Formula Used
Free Androgen Index estimates the relationship between total testosterone and sex hormone binding globulin. The standard formula is:
FAI = (Total Testosterone in nmol/L ÷ SHBG in nmol/L) × 100
This calculator first converts testosterone into nmol/L when another supported unit is selected. It then divides converted testosterone by SHBG and multiplies the result by 100. SHBG must be entered in nmol/L.
How To Use This Calculator
- Enter your total testosterone value.
- Select the unit shown on your lab report.
- Enter SHBG in nmol/L.
- Add custom reference limits from your laboratory if available.
- Select a patient group for record clarity.
- Press the calculate button.
- Review the result shown below the header.
- Export the calculation as CSV or PDF when needed.
Free Androgen Index Guide
What This Calculator Does
The Free Androgen Index Calculator helps estimate androgen availability from two common lab values. These values are total testosterone and SHBG. Total testosterone shows the measured testosterone amount. SHBG shows binding protein activity. When SHBG is high, less testosterone may be freely available. When SHBG is low, calculated availability may rise.
Why The Index Matters
FAI is often reviewed during hormone assessment. It may support discussions about acne, hair changes, cycle changes, fatigue, libido, or endocrine follow up. It is not a diagnosis. It is a calculated ratio. The result should be compared with local laboratory guidance. Medical history also matters. Medicines, age, pregnancy status, thyroid function, liver function, and insulin resistance may affect SHBG.
Unit Support
The calculator accepts testosterone in nmol/L, ng/dL, and ng/mL. It converts all supported entries into nmol/L before calculation. SHBG remains in nmol/L. This keeps the formula consistent. It also reduces manual conversion mistakes. The custom range fields help match the report you are reviewing.
Result Review
A low result can suggest lower calculated androgen availability. A high result can suggest higher calculated androgen availability. But the meaning depends on the person and the laboratory method. Different labs may use different assays. Reference intervals may also differ by sex, age, and clinical setting. Always read the result beside symptoms and professional advice.
Record Keeping
The export buttons create simple records. CSV works well for spreadsheets. PDF works well for sharing and printing. Notes can hold context from the lab report. Keep private health data secure. Do not use this tool as a replacement for medical care.
FAQs
What is Free Androgen Index?
Free Androgen Index is a calculated ratio. It compares total testosterone with SHBG. It estimates relative androgen availability.
What formula does this tool use?
It uses FAI = total testosterone in nmol/L divided by SHBG in nmol/L, then multiplied by 100.
Can I enter testosterone in ng/dL?
Yes. Select ng/dL from the unit menu. The calculator converts it into nmol/L before calculating the index.
Can I enter testosterone in ng/mL?
Yes. Select ng/mL. The calculator converts that value into nmol/L and then applies the standard FAI formula.
Does this calculator diagnose hormone disorders?
No. It only performs a calculation. Diagnosis needs symptoms, history, physical review, and professional interpretation of lab results.
Why does SHBG affect the result?
SHBG binds sex hormones in blood. Higher SHBG can lower calculated free availability. Lower SHBG can raise the calculated index.
Should I use my lab reference range?
Yes. Lab ranges can vary. Entering your report range gives a more useful comparison for your specific result.
Can I download the result?
Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple printable calculation summary.