Free & Bioavailable Testosterone Calculator
Calculate free and bioavailable testosterone using the Vermeulen formula.
Your stats
Default is usually 4.3 g/dL
Results
Enter your values to see the calculation results.
Calculations based on the Vermeulen et al. (1999) formula.
About this tool
The free and bioavailable testosterone calculator uses the Vermeulen formula to estimate free testosterone and bioavailable (free plus albumin-bound) testosterone from your total testosterone, SHBG, and albumin. It is the standard equation clinicians use when a direct free-T lab test isn't available. Enter three values and get both calculated fractions.
How to use it
- 1 Enter your total testosterone (in ng/dL or nmol/L).
- 2 Enter your SHBG (in nmol/L).
- 3 Enter your albumin (it defaults to 4.3 g/dL if you don't have it).
- 4 Read your calculated free T and bioavailable T.
Frequently asked questions
What is the Vermeulen formula?
It is the most widely used equation for estimating free testosterone from total testosterone, SHBG, and albumin. Published by Dr. Alex Vermeulen, it is the standard calculation when a direct free-T assay isn't available.
Is calculated free T as accurate as a direct lab test?
Calculated free T (Vermeulen) correlates well with direct equilibrium-dialysis assays and is often preferred because direct analog-based free-T tests are unreliable. For most clinical purposes, the calculated value is the better number.
Educational use only — not medical advice. Results are estimates based on published formulas and models.