Free TRT tool
Testosterone unit converter and free T calculator
Labs report testosterone in different units. Convert your results from one unit to another, and estimate free testosterone (the part not bound to proteins in the blood) from total testosterone, SHBG (a protein that binds testosterone) and albumin.
Convert a lab result
Type a value in any box. The other boxes in the same card change to match right away.
Total testosterone
Labs in the United States usually report ng/dL. Labs in Canada, the United Kingdom and Europe usually report nmol/L.
1 ng/dL = 0.0347 nmol/L. 1 nmol/L = 28.84 ng/dL.
Free testosterone
Often reported in pg/mL or pmol/L. Some labs use ng/dL or nmol/L.
1 pg/mL = 3.467 pmol/L. 1 ng/dL = 10 pg/mL.
Estradiol (E2)
The main form of estrogen. Reported in pg/mL or pmol/L.
1 pg/mL = 3.671 pmol/L.
Hematocrit
The share of your blood made up of red blood cells. Some labs print it as a fraction, such as 0.45 L/L.
0.45 L/L = 45%.
SHBG
Sex hormone binding globulin, a protein that carries testosterone in the blood.
Labs report SHBG in nmol/L almost everywhere, so there is nothing to convert. Use the number from your report in the free testosterone calculator below.
Estimate free testosterone
Enter total testosterone and SHBG from the same blood test. Albumin is optional. If your report does not show it, the calculator uses the average of 4.3 g/dL.
Your estimate
Enter your numbers to see the result.
Guideline cut-offs for low testosterone
Medical guidelines use different cut-offs for low testosterone. This table shows each one in both units, so you can compare the numbers. It does not place your own result in any group.
Total testosterone
9.2 nmol/L(converted)264 ng/dL
The lower limit of the normal range in healthy young men without obesity, for tests certified to the CDC standard (the US Centers for Disease Control and Prevention).
CUA (Canadian Urological Association, 2021)
10 nmol/L288 ng/dL(converted)
Described as a reasonable threshold for diagnosis, based on a morning blood test (7 to 11 am).
AUA (American Urological Association, 2018)
10.4 nmol/L(converted)300 ng/dL
A reasonable cut-off to support a diagnosis of low testosterone.
Endocrine Society statement (2026)
10.4 nmol/L(converted)300 ng/dL
A public statement, not a full guideline. It calls a level near this value a common clinical threshold, based on at least two early-morning fasting tests.
EAU (European Association of Urology, 2026)
12 nmol/L346 ng/dL(converted)
A threshold to diagnose low testosterone that starts later in life. The EAU also writes it as 3.5 ng/mL, a rounded form of the same amount.
ICSM (International Consultation on Sexual Medicine, 2024)
12 nmol/L346 ng/dL(converted)
A threshold to diagnose low testosterone that starts later in life. The ICSM asks for fasting morning tests, repeated at least twice below this level before treatment.
BSSM (British Society for Sexual Medicine, 2023)
12 nmol/L346 ng/dL(converted)
Based on two separate morning tests (8 to 11 am). The BSSM gives this as the level below which treatment is usually needed. A low free testosterone result (see below) can be used instead.
Primary care consensus sponsored by the Androgen Society (2026)
12 nmol/L346 ng/dL(converted)
An international expert consensus for primary care. It considers total testosterone below this level low, and also asks for symptoms or signs before treatment. Only its summary (abstract) was available to check.
Free testosterone
EAU (European Association of Urology, 2026)
220 pmol/L63.5 pg/mL(converted)
A threshold for calculated free testosterone, for when SHBG is higher or lower than usual. The EAU notes that the evidence for it is limited.
BSSM (British Society for Sexual Medicine, 2023)
225 pmol/L64.9 pg/mL(converted)
Based on two separate morning tests (8 to 11 am). The BSSM gives this as the level below which treatment is usually needed, alongside its total testosterone value of 12 nmol/L.
- The AUA, the EAU and the BSSM ask for at least two morning blood tests before a diagnosis or treatment. The AUA also asks for symptoms or signs. One number alone does not make a diagnosis.
- Most rows are cut-offs used for diagnosis or for starting treatment. None of them is a target for treatment.
- “Converted” means the guideline did not state that unit. The value was converted with the factors above and rounded.
Checked against each guideline on September 27, 2026.
How it works
Converting units
Labs report hormones either by weight (ng/dL, pg/mL) or by the number of molecules (nmol/L, pmol/L). To switch between the two, the converter uses the weight of one mole (a fixed, very large number of molecules): 288.42 grams for testosterone and 272.38 grams for estradiol. That gives the factors shown in each card.
Estimating free testosterone
Most testosterone in the blood is carried by two proteins. SHBG holds it tightly. Albumin holds it loosely. Only a small part is free. The Vermeulen equation uses how strongly each protein holds testosterone to estimate the free part from your total testosterone, SHBG and albumin.
Bioavailable testosterone
Albumin lets go of testosterone easily. So some labs add the free part and the part held by albumin together and call it bioavailable testosterone.
The formula (all amounts in mol/L)
N = 1 + Ka × [albumin] a = Kt × N b = N + Kt × ([SHBG] − [TT]) FT = (−b + √(b² + 4 × a × [TT])) ÷ (2 × a) Bioavailable T = FT × N
Method: Vermeulen A, Verdonck L, Kaufman JM. J Clin Endocrinol Metab 1999;84:3666-72
Constants
- Kt, how strongly SHBG binds testosterone: 1.0 × 10⁹ L/mol
- Ka, how strongly albumin binds testosterone: 3.6 × 10⁴ L/mol
- Albumin molecular weight: 69,000 g/mol
- Albumin if you do not change it: 4.3 g/dL, the average the method uses
- [TT] is total testosterone and FT is free testosterone.
Limits of the estimate
- The result is an estimate. The Endocrine Society (2018) says free testosterone should be measured by equilibrium dialysis (a direct lab method) or estimated with a formula that matches that method.
- The Endocrine Society also notes that a single agreed normal range for free testosterone has not been set.
- The estimate is only as good as the numbers you enter. Total testosterone and SHBG tests can differ from one lab to another.
- Other calculators may use other formulas or constants, so their results can differ.
Terms used on this page
- ng/dL
- Nanograms per deciliter. A common unit for testosterone blood tests in the United States.
- nmol/L
- Nanomoles per liter. The unit used for testosterone blood tests in Canada, the United Kingdom, Europe and Australia.
- Total testosterone
- All the testosterone in a blood sample: the part held by proteins and the free part.
- Free testosterone
- The small part of testosterone in the blood that is not held by any protein.
- Bioavailable testosterone
- Free testosterone plus the testosterone loosely held by albumin.
- SHBG
- Sex hormone binding globulin. A protein made by the liver that holds testosterone tightly in the blood.
- Albumin
- The most common protein in the blood. It holds testosterone loosely.
- Estradiol
- The main form of estrogen. Men make it too, mostly from testosterone.
- Hematocrit
- The share of your blood made up of red blood cells, shown as a percent or as a fraction (L/L).
- pg/mL and pmol/L
- Picograms per milliliter and picomoles per liter. Units for very small amounts, such as free testosterone and estradiol. A picogram is one thousandth of a nanogram.
Sources
The method, constants and conversion factors come from these sources. The guideline cut-offs follow.
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab 1999;84:3666-72
- Free and bioavailable testosterone calculator, Hormonology department, University Hospital of Ghent (hosted by ISSAM)
- Chung MC, Gombar S, Shi RZ. Implementation of Automated Calculation of Free and Bioavailable Testosterone in Epic Beaker Laboratory Information System. J Pathol Inform 2017;8:28
- PubChem. Testosterone (CID 6013)
- PubChem. Estradiol (CID 5757)
- Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline
- Canadian Urological Association guideline on testosterone deficiency in men: Evidence-based Q&A
- Evaluation and Management of Testosterone Deficiency: AUA Guideline
- Statement on Testosterone Replacement Therapy (Endocrine Society press statement, 16 July 2026)
- EAU Guidelines on Sexual and Reproductive Health, Chapter 3: Male Hypogonadism (2026 edition)
- Male hypogonadism: recommendations from the Fifth International Consultation on Sexual Medicine (ICSM 2024)
- The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice
- Managing testosterone deficiency in primary care: an international expert consensus