Free Testosterone Calculator

This tool estimates free and bioavailable testosterone from a total testosterone result, SHBG and albumin, using the Vermeulen equation and the association constants published with it. Enter the three laboratory values in whichever units your report uses and it returns free testosterone in ng/dL, pg/mL, nmol/L and pmol/L, the bioavailable figure, both as a percentage of total, and the free androgen index alongside for comparison. A second action runs the same equation backwards to show what total testosterone a given free level corresponds to at your SHBG. The result is a calculated estimate rather than a measurement, and it is not the same quantity as a laboratory free testosterone by equilibrium dialysis. Reference ranges are specific to the assay and the laboratory, so read any value against the range printed on your own report and take the interpretation from the clinician who ordered the test.

Calculator Type
Total Testosterone Unit
Albumin Unit
The total testosterone figure from the report, with its unit picked below.
Sex hormone binding globulin, as the laboratory reports it. This is almost always given in nmol/L.
Leave it alone to use 4.3 g/dL, the reference value the published equation assumes. Use your own figure if you have one.
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Free Testosterone Unit
Albumin Unit
The free testosterone figure you are aiming at, with its unit picked below.
Sex hormone binding globulin, as the laboratory reports it. This is almost always given in nmol/L.
Leave it alone to use 4.3 g/dL, the reference value the published equation assumes. Use your own figure if you have one.
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