Testosterone unit converter

Testosterone conversion table

The values people most often need, both directions. 264 ng/dL and 12 nmol/L appear because they are guideline thresholds rather than round numbers.

All hormone conversion factors

Every factor below is derived from molecular weight, so they are exact rather than estimated. The commonest error on this table is not the arithmetic - it is reading the wrong unit off the lab report in the first place.

Reference ranges and guideline thresholds

These are not the same thing, and conflating them causes a great deal of unnecessary worry. A reference range describes what is typical in a healthy population. A diagnostic threshold is where a guideline body suggests investigating - a policy decision informed by that data, not a fact derived from it.

Ranges converted here for convenience; each source publishes in its own unit system. Your own lab will also print its own reference interval, which may differ from all of these because it reflects that lab's assay and its own reference population.

Why two labs disagree when the maths does not

The conversion is fixed arithmetic, so when two results seem irreconcilable the cause is somewhere else. Four candidates, roughly in order of how often they are the culprit:

• Time of day. Testosterone follows a diurnal rhythm, peaking in the morning. This is why guidelines specify a morning draw, and why an afternoon result is not comparable to a 8am one from a month earlier.
• Assay platform. Immunoassay and LC-MS/MS measure differently. The gap is most consequential for estradiol in men and for free testosterone, where a "sensitive" assay is generally the one worth having.
• Calculated vs measured free T. Many reports calculate free testosterone from total T, SHBG and albumin rather than measuring it. Different calculation methods give different answers from identical inputs, so a calculated value and a measured one are not interchangeable.
• Where you are in the injection cycle. On an injected protocol the level is a moving curve, not a fixed number. A trough draw and a peak draw from the same protocol can differ by a factor of two or more - which is exactly why when you drew the blood is as important as the number it produced.

None of these are errors in the lab work. They are the reason a single number is a poor basis for a decision, and a trend measured consistently is a much better one.

Frequently asked questions

How do I convert testosterone from nmol/L to ng/dL?

Multiply nmol/L by 28.84. So 12 nmol/L is about 346 ng/dL, 15 nmol/L is about 433 ng/dL, and 20 nmol/L is about 577 ng/dL. Going the other way, multiply ng/dL by 0.0347. The factor comes from testosterone's molecular weight of 288.42 g/mol - it is fixed arithmetic, not an approximation, so the conversion itself is never the source of disagreement between two results.

Why does my UK lab report nmol/L when US forums use ng/dL?

They are the same measurement in different unit systems. Most of Europe, the UK, Australia and Canada report in SI units (nmol/L), while the United States mostly uses conventional mass units (ng/dL). Neither is more accurate. This is the single biggest source of confusion in international TRT discussions: someone reporting '15' and someone reporting '433' may have identical testosterone levels.

What is a normal testosterone level?

The most defensible modern answer is the CDC-standardised harmonised range from Travison et al. (JCEM, 2017): 264-916 ng/dL, or roughly 9.2-31.8 nmol/L, in healthy non-obese men aged 19-39. Guideline diagnostic thresholds differ from that range and from each other - the Endocrine Society uses 264 ng/dL, the AUA uses 300 ng/dL, and the EAU uses 12 nmol/L (about 346 ng/dL). A result can therefore be 'low' by one guideline and 'normal' by another without anyone being wrong.

How do I convert estradiol from pg/mL to pmol/L?

Multiply pg/mL by 3.67. So 30 pg/mL is about 110 pmol/L. To go back, multiply pmol/L by 0.272. Note that the conversion is the easy part of estradiol - the harder issue is assay type. A standard immunoassay and an LC-MS/MS 'sensitive' estradiol assay can return substantially different numbers on the same sample, and in men the sensitive assay is the one generally considered reliable.

Can I compare two results from different labs?

Only with care, and unit conversion is the smallest part of it. Different assay platforms measure testosterone differently, and each lab publishes its own reference interval - which is why the harmonised CDC-standardised range exists as a common yardstick. If you are tracking a trend over time, using the same lab and the same assay matters more than any single number, as does keeping the draw time consistent, since testosterone follows a diurnal rhythm and morning draws are the convention.

Does the conversion factor change for free testosterone?

The molecular weight is the same, but the units usually are not. Free testosterone is typically reported in pg/mL rather than ng/dL, so the factor to pmol/L is 3.467. If your lab reports free testosterone in ng/dL, multiply by 34.67 to get pmol/L. Check which unit is on your report before converting - mixing up pg/mL and ng/dL is a factor-of-100 error and by far the most common mistake on this particular value.

Sources & further reading

• Travison TG et al., Harmonized reference ranges for circulating testosterone levels in men (JCEM 2017) - source of the CDC-standardised 264–916 ng/dL range
• Bhasin S et al., Testosterone therapy in men with hypogonadism - Endocrine Society Clinical Practice Guideline (2018)
• AUA Guideline - Testosterone Deficiency (300 ng/dL diagnostic threshold)
• EAU Guidelines - Sexual and Reproductive Health (12 nmol/L threshold)
• CDC Hormone Standardization Program (HoSt) - why assay standardisation is needed for cross-lab comparison
• OptiPin tools: free testosterone calculator · bloodwork guide · free vs total T · forecast methodology

Conversion factors are computed from molecular weights (testosterone 288.42, estradiol 272.38, DHT 290.44 g/mol) rather than copied from secondary sources, so they can be re-derived rather than taken on trust. Guideline thresholds are quoted as published and linked to their source; where guidelines disagree we have shown all of them rather than picking one.

Not medical advice. This is a unit-conversion reference. Interpreting a hormone result requires clinical context this page does not have - symptoms, history, timing, assay, and repeat testing. Do not start, change, or stop treatment based on a converted number.