Bioavailable Testosterone Calculator

The Bioavailable Testosterone Calculator estimates your active hormone levels using Total Testosterone, SHBG, and Albumin. This calculator provides information to help determine how much testosterone is free for your body to use. Whether you're assessing symptoms of low T, monitoring TRT progress, or optimizing fitness, this tool provides a clinical-grade estimate.

ng/dL (Range: 50-2000)
nmol/L (Range: 5-250)
g/dL (Range: 2.0-6.0)

How Bioavailable Testosterone Is Calculated

Bioavailable testosterone represents the "free" testosterone plus the testosterone weakly bound to albumin. Only this fraction is biologically active and able to enter cells to function.

This calculator uses the Vermeulen Equation, a widely accepted clinical standard for calculating free and bioavailable testosterone. This method accounts for the binding affinity of SHBG and albumin.

BioT = Free Testosterone + (Free T × Kalb × [Albumin])

Where:

  • Free T is calculated using Total T, SHBG, and Albumin concentrations.
  • Kalb is the association constant for Albumin (3.6 × 104 L/mol).
  • Concentrations are converted to molar units for accuracy before being converted back to ng/dL.

What Your Bioavailable Testosterone Means

Your Bioavailable Testosterone level indicates how much active hormone is available to your tissues. A high total testosterone level with high SHBG can still result in low bioavailable testosterone, causing symptoms of low T.

Interpreting Your Calculation

In healthy adult men, Bioavailable testosterone typically ranges from 200 to 500 ng/dL, though this varies by age. Levels below 150 ng/dL often correlate with symptoms like fatigue, low libido, and muscle loss.

For High SHBG: If your Total T is normal but Bio T is low, high SHBG may be "hogging" your testosterone. Lifestyle changes or medication can sometimes lower SHBG.

For Monitoring: If you are on Testosterone Replacement Therapy (TRT), monitoring Bio T provides a better picture of therapeutic success than Total T alone.

Calculation logic verified using publicly available standards.

View our Accuracy & Reliability Framework →