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Testosterone Level Calculator

Calculate your free testosterone from total testosterone, SHBG and albumin using the Vermeulen equation.

Default: 43 g/L. Adjust only if you know your albumin (e.g. from blood panel).

Reference ranges (adult men)

MarkerRangeInterpretation
Total testosterone8.6 – 29.0 nmol/LNormal — no action needed
Total testosterone< 8 nmol/LPossible hypogonadism
Free testosterone200 – 620 pmol/LNormal — no action needed
Free testosterone< 200 pmol/LPossible hypogonadism

How it works

This calculator uses the Vermeulen equation (Vermeulen et al., JCEM 1999) to compute free testosterone from total testosterone, SHBG and albumin. In blood, only about 1–3 % of total testosterone is biologically active (free) — the rest is bound to SHBG (~44 %) or albumin (~54 %). The formula solves a quadratic with binding constants KT (SHBG) = 1·10⁹ L/mol and KA (albumin) = 3.6·10⁴ L/mol. Adult-male reference ranges: total 8.6–29 nmol/L, free 0.20–0.62 nmol/L (200–620 pmol/L). Total testosterone below 8 nmol/L is classified as hypogonadism per the Endocrine Society guideline.

This calculator is not a medical diagnosis. If your values are low or you have symptoms of testosterone deficiency (fatigue, low libido, muscle loss), please see a doctor.

Frequently Asked Questions

What is free testosterone?+
Free testosterone is the unbound, biologically active fraction of your testosterone. Only about 1–3 % circulates freely — the rest is bound to SHBG (sex hormone-binding globulin) or albumin and is physiologically less active.
Why isn't total testosterone enough?+
If total testosterone is normal but SHBG is high, free testosterone may be in deficit. Symptoms of low testosterone often correlate better with free testosterone than with the total.
When should I get tested?+
In the morning between 7–10am (peak), fasting, after good sleep. If hypogonadism is suspected (fatigue, low libido, muscle loss), do two separate-day measurements.
What affects SHBG?+
SHBG rises with hyperthyroidism, liver disease, estrogen therapy, and age. SHBG drops with obesity, insulin resistance, hypothyroidism, and Cushing's syndrome.
What do low values mean?+
Total testosterone below 8 nmol/L (≈ 230 ng/dL) is classified as hypogonadism per the Endocrine Society guideline (2018). 8–12 nmol/L is a gray zone — combine with clinical symptoms and free testosterone.
Can I raise testosterone naturally?+
Resistance training (especially compound lifts), 7–9 hours of sleep, sufficient vitamin D and zinc, weight loss if overweight, reduced alcohol. These measures raise testosterone by 10–20 % in deficient men.

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Testosterone Level Calculator: Free vs Bound, SHBG and What Your Numbers Mean

8 min