Helvy tool
Free Testosterone Calculator
Total testosterone can read normal while the usable, free fraction is low, because SHBG binds most of it. Enter your total testosterone and SHBG to see your calculated free and bioavailable testosterone.
How this is worked out
Calculated by the Vermeulen (1999) equilibrium method, the same model used by the ISSAM free-testosterone calculator: association constants 1.0 x 10⁷ L/mol (SHBG) and 3.6 x 10⁴ L/mol (albumin), with serum albumin defaulting to 43 g/L. This is the Vermeulen model, not the Tru-T model, so it matches Vermeulen-based calculators. nmol/L to ng/dL uses a factor of 28.842.
This tool is for general wellbeing information and is not a diagnosis or medical advice. It places the numbers you enter in context; it cannot tell you whether you have a condition. If a result concerns you, or you have symptoms, speak to your GP.
Measure it properly
A calculator works on numbers you already have. The Complete Male Hormones panel is processed by a UKAS-accredited lab and reviewed by a qualified clinician.
See the Complete Male Hormones panel