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Free Testosterone from Total T and SHBG (Vermeulen) Calculator

Quadratic Vermeulen approximation with K_SHBG = 1·10⁹ M⁻¹.

Compute the free testosterone fraction from total testosterone (nmol/L), sex-hormone-binding globulin (nmol/L), and serum albumin (g/L) using a simplified Vermeulen quadratic that assumes a constant SHBG-T binding affinity (~1 × 10⁹ M⁻¹) and an albumin-T binding affinity (~3.6 × 10⁴ M⁻¹). Reports free testosterone in pmol/L and percent of total.

Priya Venkatesan By Priya Venkatesan
Published Last reviewed 1 min read

Inputs

nmol/L
nmol/L
g/L

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Vermeulen quadratic for [T_free] given [T_total], [SHBG], [Alb].

In depth

Compute the free testosterone fraction from total testosterone (nmol/L), sex-hormone-binding globulin (nmol/L), and serum albumin (g/L) using a simplified Vermeulen quadratic that assumes a constant SHBG-T binding affinity (~1 × 10⁹ M⁻¹) and an albumin-T binding affinity (~3.6 × 10⁴ M⁻¹). Reports free testosterone in pmol/L and percent of total.