If you’ve had blood tests for testosterone, you’ve probably only been given a total testosterone result. But total T doesn’t always tell the full story.
Our free & bioavailable testosterone calculator uses your total testosterone, SHBG and albumin to estimate the amount of hormone that is actually available for your body to use – calculated using the Vermeulen equation, in line with UK (PCTAG/BSSM) practice.
Important: This tool is for information only and doesn’t replace a consultation with a qualified doctor. Never start, stop or change testosterone treatment based on an online calculator alone.
• Use the value from your lab report (usually in g/L).
• If your result is in g/dL, you can switch the unit in the dropdown.
• This is usually labelled “SHBG” or “Sex Hormone Binding Globulin” on your report.
• Choose the correct unit (nmol/L, ng/dL or ng/mL) that matches your lab report.
• The calculator automatically converts everything into nmol/L for you.
You’ll see:
• Free testosterone (nmol/L)
• Bioavailable testosterone (nmol/L)
• Free T % and bioavailable T % of your total testosterone
This calculator uses the Vermeulen method for educational purposes only and does not replace personalised medical advice. Always interpret results with a qualified clinician.
This is the number most labs report. It includes:
Total testosterone is useful, but it doesn’t show how much hormone is actually available to your tissues.
Free testosterone is the unbound fraction of testosterone circulating in the blood. It:
Our calculator estimates free testosterone using the Vermeulen equation, taking SHBG and albumin into account.
Bioavailable testosterone is: Free testosterone + albumin-bound testosterone
Albumin holds testosterone relatively loosely, so this portion is still considered available for use by the body. Many clinicians look at bioavailable T alongside total and free testosterone when assessing androgen status.
Don’t ignore the symptoms of low testosterone. Our home test kit is the first step to getting answers and taking back control of your health. Order online today and start your TRT journey with Men’s Medical Clinic Leeds.
If you're unsure, have symptoms you're worried about, or want to ask about specific treatment options, you can book a free 15-minute call directly with Dr Areeb Mazhar. No pressure, no obligation — just clear answers from a doctor who specialises in men's health.
While an online testosterone calculator is useful, there are important caveats:
If your results are borderline or confusing, you should speak to a doctor who understands male hormones and can interpret them in context.
