Free testosterone calculator

Here you can easily calculate the bioactive testosterone circulating in plasma by using our free testosterone calculator. These calculated parameters more accurately reflect the level of bioactive testosterone than the sole measurement of total serum testosterone does.

Enter the arithmetic units into the fields below to calculate the testosterone level 

Free Testosterone

Biovailable Testosterone

Using our testosterone calculator is an accurate way to calculate the testosterone in blood serum. The given parameters are reflecting the amount of bioactive testosterone in a more accurate way than the common measurements to calculate the testosterone.

Additional information

A symptomatic response to testosterone therapy is generally seen within 3 months. Monitoring should occur at least 2-3 times during the first year, and 1-2 times per year thereafter. Monitoring should include serum testosterone, PSA levels, and haematocrit. There is no need to measure liver or renal function tests for any of the routine testosterone therapy formulations.1

Using a value of 3.6 x 104 L/mol for the association constant of albumin for testosterone, the calculated albumin-bound testosterone varied from 7.14 nmol/L (40 g/L albumin) to 7.80 nmol/L (50 g/L albumin). In view of the relatively unimportant changes in FT, when the albumin concentration varies by as much as 25%, it was concluded that for routine purposes FT could be calculated assuming an albumin concentration of 43 g/L (6.2 x 10-4 mol/L) if one is not dealing with sera from patients with marked abnormalities in plasma protein composition, such as in nephrotic syndrome or cirrhosis of the liver, or with sera obtained during pregnancy, in which cases the actual albumin concentration should be taken into account.2


1. Traish et al. Testosterone Deficiency, The American Journal of Medicine (2011) 124, 578-587

2. Vermeulen et al., A critical evaluation of simple methods for the estimation of free testosterone in serum, J Clin Endocrinol Metab (1999) 84(10): 3666-72

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