This free testosterone calculator will help you determine your free testosterone levels and bioavailable testosterone. If you need help understanding your free testosterone levels and optimising them with TRT then get in touch, we have over 20 years experience in TRT and hormone rebalancing/optimisation.
Testosterone Units Conversion Tool
Click here for our testosterone unit conversion tool.
Find out more about TRT in the UK
TRT UK Guide
How to use this free testosterone calculator
Assuming you have had your testosterone blood testing done you may want to use our calculation tools to help you understand your results.
Total Testosterone is only part of the picture. If you let your doctor tell you that everything is fine or you are normal and they haven’t measured or calculated your FREE TESTOSTERONE, then your at risk of being misdiagnosed, and will continue to suffer through with symptoms of low testosterone levels.
Free Testosterone is the portion of unbound male hormone that is free from binding proteins.
Our calculator will help you either estimate or accurately determine what your Free Testosterone level is.
You will need the following in order to calculate:
Albumin:
This is a protein that weakly binds to your testosterone. The albumin and testosterone bound together is called bioavailable testosterone.
This complex can become more easily disassociated than the Testosterone bound to SHBG or sex hormone binding globulin.
Make sure you have the correct units before entering the albumin into the calculator. Albumin in the UK is normally expressed as g/L and the average is around 43g/L.
If you do not know your albumin level then use the preset number of 43 g/L.
SHBG:
This is the sex hormone binding globulin and this is expressed in the units nmol/L
Testosterone:
This is the Total Testosterone and this is used to calculate your free testosterone based on the albumin and the SHBG levels.
What is Bioavailable Testosterone?
Bioavailable testosterone is the part of testosterone in the blood that the body can actually use. Testosterone travels through the bloodstream in three main forms. A large portion is bound very tightly to a protein called sex hormone binding globulin, which makes it unavailable to the tissues. A smaller portion binds more loosely to albumin, a common blood protein, and a very small fraction remains completely free.
The term bioavailable testosterone refers to the combination of free testosterone and albumin bound testosterone. Because albumin binding is weak and reversible, this fraction is able to leave the bloodstream and enter tissues, where it can attach to androgen receptors.
This active portion is responsible for the hormone’s key functions, including supporting muscle and bone strength, regulating libido and mood, and maintaining male sexual characteristics. Clinically, bioavailable testosterone is often a more useful measure than total testosterone, especially in cases where levels of sex hormone binding globulin are abnormally high or low. In those situations, total testosterone may appear within the normal range, while the actual amount available to the body is not.
Bioavailable Testosterone vs Free Testosterone: What is the difference?
Free testosterone is the very small fraction of testosterone in the bloodstream that circulates completely unbound. It is not attached to any proteins and can immediately move into tissues to activate androgen receptors. Although it represents only about two to four percent of total testosterone, it is considered the most direct measure of the hormone’s immediate activity.
Bioavailable testosterone includes free testosterone plus the fraction that is loosely bound to albumin. Because albumin binding is weak and reversible, this portion can also enter tissues and act on androgen receptors. Bioavailable testosterone therefore represents a larger pool of testosterone available for use by the body than free testosterone alone.
Optimal Testosterone Levels
Measurements in SI Units (nmol/L) | ||||||
| Age | Total Test | Stand Dev | Free Test | Stand Dev | SHBG | Stand Dev |
| 25-34 | 21.4 | 5.9 | 0.43 | 0.10 | 35.5 | 8.8 |
| 35-44 | 23.1 | 7.4 | 0.36 | 0.04 | 40.1 | 7.9 |
| 45-54 | 21 | 7.4 | 0.31 | 0.08 | 44.6 | 8.2 |
| 55-64 | 19.5 | 6.8 | 0.29 | 0.07 | 45.5 | 8.8 |
| 65-74 | 18.2 | 6.8 | 0.24 | 0.08 | 48.7 | 14.2 |
| 75-83 | 16.3 | 5.8 | 0.21 | 0.08 | 51.0 | 22.7 |
| 85-100 | 13 | 4.6 | 0.19 | 0.08 | 65.9 | 22.8 |
Measurements in Conventional Units (ng/dl) SHBG in (nmol/L) | ||||||
| Age | Total Test | Stand Dev | Free Test | Stand Dev | SHBG | Stand Dev |
| 25-34 | 617 | 170 | 12.3 | 2.8 | 35.5 | 8.8 |
| 35-44 | 668 | 212 | 10.3 | 1.2 | 40.1 | 7.9 |
| 45-54 | 606 | 213 | 9.1 | 2.2 | 44.6 | 8.2 |
| 55-64 | 562 | 195 | 8.3 | 2.1 | 45.5 | 8.8 |
| 65-74 | 524 | 197 | 6.9 | 2.3 | 48.7 | 14.2 |
| 75-83 | 471 | 169 | 6.0 | 2.3 | 54.0 | 22.7 |
| 85-100 | 376 | 134 | 5.4 | 2.3 | 65.9 | 22.8 |
Normal Testosterone Levels in men (non-diabetic)
Measurements in SI Units (nmol/L) | ||||||
| Age | Total Test | Stand Dev | Median TT | 5th % | 10th % | 95th % |
| <25 | 24.0 | 5.5 | 24.2 | 14.2 | 16.2 | 33.1 |
| 25-29 | 23.2 | 7.1 | 22.1 | 13.5 | 15.2 | 34.8 |
| 30-34 | 21.5 | 6.7 | 20.7 | 12.1 | 13.5 | 33.8 |
| 35-39 | 20.7 | 6.6 | 19.7 | 11.4 | 13.5 | 32.8 |
| 40-44 | 20.7 | 6.9 | 20.7 | 11.0 | 13.1 | 32.4 |
| 45-49 | 18.9 | 5.7 | 18.3 | 11.4 | 12.4 | 29.3 |
| 50-54 | 18.9 | 6.5 | 17.9 | 10.0 | 12.1 | 32.4 |
| 55-59 | 19.1 | 6.0 | 19.0 | 11.0 | 11.7 | 30.0 |
Source: Androgens and the Aging Male – B.J. Oddens, A. Vermeulen
If you are looking to get your testosterone levels optimised and are thinking about how to get TRT, consider speaking to us today.
