These calculations more accurately reflect the level of bioactive testosterone than does the measurement of total testosterone. Testosterone and dihydrotestosterone (DHT) circulate in plasma unbound (averaging 2 – 3%), bound to sex hormone-binding globulin (SHBG) and weakly bound to albumin. The SHBG-bound fraction is biologically inactive because of the high binding affinity of SHBG for testosterone.

Bioavailable testosterone includes free testosterone plus testosterone bound to albumin.

Free & Bioavailable Testosterone calculator

Free Testosterone
Bioavailable Testosterone

Disclaimer: Results from this calculator should NOT be solely relied upon in making (or refraining from making) any decision in any case/ circumstances without the prior consultation of experts or professional persons. No responsability whatsoever is assumed for its correctness or suitability for any given purpose.

WARNING! The calculated free and bioavailable testosterone are reliable in most clinical situations, but should not be relied upon in situations with potential massive interference by steroids binding to SHBG; e.g. in women during pregnancy, in men during treatment inducing high levels of DHT (e.g. transdermal DHT, oral testosterone) or mesterolon

Journal of Clinical Endocrinology and Metabolism

Stephanie T. Page, John K. Amory, F. DuBois Bowman, Bradley D. Anawalt, Alvin M. Matsumoto, William J. Bremner, J. Lisa Tenover, Exogenous Testosterone (T) Alone or with Finasteride Increases Physical Performance, Grip Strength, and Lean Body Mass in Older Men with Low Serum T, The Journal of Clinical Endocrinology & Metabolism, Volume 90, Issue 3, 1 March 2005, Pages 1502–1510,