Testosterone Unit Converter

Testosterone conversion table

One nmol/L is 28.842 ng/dL. To go from nmol/L to ng/dL, multiply by 28.842. To go from ng/dL to nmol/L, divide by the same number. So 12 nmol/L is 346 ng/dL, and 300 ng/dL is 10.40 nmol/L. The first table lists every whole number from 1 to 40 nmol/L, and the second every 50 ng/dL up to 1,200.

Values are rounded. The converter above handles any figure, including decimals. Once you have the number in the right unit, our guide to what a converted testosterone result means in the UK sets it against the thresholds British clinicians use, and testosterone levels by age breaks it down by decade.

Is that number low? The UK and the US draw the line in different places

Most people convert a testosterone result for one reason. They have a UK report in nmol/L and they are reading an American chart in ng/dL. The two are measuring the same thing. They just put the low line somewhere different, in different units, which is how the same blood can read normal on one page and borderline on the next.

Look at the first two rows. The American cut-off of 300 ng/dL works out at 10.4 nmol/L, which is lower than the UK figure of 12. So a man who reads 11 nmol/L, or 317 ng/dL, is above the American line and below the British one. Same sample. Two answers.

The UK figure is the British Society for Sexual Medicine threshold, set out in its 2023 guidance on male testosterone deficiency. It asks for two separate morning samples, taken between 8am and 11am, before anyone reads much into one number.

“Clinicians should use a total testosterone level below 300 ng/dL as a reasonable cut-off in support of the diagnosis of low testosterone.”

— American Urological Association, Testosterone Deficiency Guideline, statement 1

Note the words that guideline uses. A cut-off “in support of” a picture, not a verdict on its own. Both bodies say the same thing in the end. One reading settles nothing.

Three things move the number before any of this applies. Time of day is the big one, because testosterone peaks in the early morning and drifts down through the day. Illness pulls it down. So does a night of bad sleep. That is why both guidelines ask for a morning sample, and why the second sample matters as much as the first.

Converting the unit does not tell you whether your level is low. It only changes the unit. Where your figure sits depends on your age, your symptoms, the hour the sample was taken and the hormones read alongside it, which is a job for a qualified clinician. Our guide to normal testosterone levels by age sets the number in context, and the men’s hormones hub covers what sits around it.