/CALCULATOR
Free Testosterone
Calculator
Calculate free T from total T, SHBG, and albumin using the Vermeulen equation — the standard used in most clinical labs and the same math the MyTRT app uses.
typical 200 – 1500
typical 5 – 100
typical 3.5 – 5.5
/RESULT
Enter total T, SHBG, and albumin above to calculate.
/HOW_IT_WORKS
The Vermeulen equation models testosterone equilibrium in serum: total T is distributed between SHBG-bound (tight), albumin-bound (weak), and free fractions. Given known binding constants, the equation solves for the free fraction.
For most men on TRT, calculated free T from this method correlates with direct-dialysis measurements within ~15–20% — better than most automated immunoassays.
/INTERPRETATION
- +Reference range for adult males: ~9–30 pg/mL.
- +Most TRT clinicians target the upper third (20–30 pg/mL) for symptomatic optimization.
- +Below 9 pg/mL is generally considered deficient regardless of total T.