CalculatorsHormonesFree testosterone calculator
Free testosterone calculator
Work out the share of your testosterone that's actually free, from the total and SHBG on your report.
9.0ng/dL
Above that line
Above the line some guidelines use. Your lab prints its own range, and that's the one to read it against.
- Free testosterone
- 8.98 ng/dL311 pmol/L
- Share that's free
- 2.0%Usually about 1 to 3%
- Bioavailable
- 210 ng/dLFree plus albumin-bound
See the working
Vermeulen: solve for free T, with Kt = 1×10⁹ L/mol for SHBG and Ka = 3.6×10⁴ L/mol for albuminTotal 15.6 nmol/L, SHBG 35 nmol/L, albumin 4.3 g/dL → 0.311 nmol/LWhy free testosterone matters
Most testosterone in your blood is bound. A large share is tightly held by SHBG, some is loosely held by albumin, and only about 1 to 3% is free. Two men with the same total can have quite different free levels, because their SHBG differs.
This matters most when total testosterone is borderline, or when SHBG is unusual. SHBG rises with age and with some thyroid and liver conditions, and falls with higher body weight.
Getting a number you can trust
Testosterone runs highest in the morning, so have it drawn before 10, and repeat a low result before reading much into it. Direct free testosterone tests are often inaccurate, and that's why the calculated version is so widely used. It relies on the total and SHBG being measured well.
Questions
What's a normal free testosterone?
It depends on the lab and on your age, so use the range on your report. One European guideline suggests that around 6.5 ng/dL (225 pmol/L) free testosterone may be low in men, alongside symptoms.
I don't have albumin. Can I still use this?
Yes. 4.3 g/dL is the standard stand-in, and the result barely moves unless your albumin is unusual.
Does this work for women?
The arithmetic does. The ranges are much lower and differ by lab, so we don't draw a gauge. Read it against your report.
Does LifeFrom prescribe testosterone?
No. LifeFrom reads your results and helps you with what moves them. Treatment is a conversation for you and your doctor.
Sources
Written by LifeFrom from the sources above, and not yet reviewed by a clinician. An estimate for your own understanding: it doesn't diagnose or treat anything, and it doesn't replace your doctor.
