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

Multiply ng/dL by 0.0347, or divide by 28.84. A total testosterone of 500 ng/dL is 17.34 nmol/L; 300 ng/dL is 10.40 nmol/L; 900 ng/dL is 31.20 nmol/L. The factor is the molar mass of testosterone, 288.42 g/mol, rearranged — nothing about it depends on your laboratory or your assay.

What is 500 ng/dL of testosterone in nmol/L?

17.34 nmol/L, or 17.35 nmol/L if you use the rounded 0.0347 factor that journals print. Both round to 17.3 nmol/L at the precision a report would state. In ng/mL the same result is 5.0 ng/mL. For context, 500 ng/dL sits just below the 531 ng/dL median of the harmonized reference range for healthy non-obese men aged 19–39.

Is the 0.0347 testosterone conversion factor wrong?

Not wrong, but it is a rounding rather than a measurement, and it is very slightly high. Derived from the molar mass the factor is 0.0346717, and NIST's standard atomic weight intervals put it somewhere between 0.0346684 and 0.0346741 — so 0.0347 sits 0.075% above the top of the permitted range. What that costs at a real result is 0.014 nmol/L on a 500 ng/dL reading, or 0.41 ng/dL read back. It has never changed a clinical decision. Use it.

What is 10 nmol/L of testosterone in ng/dL?

288.4 ng/dL. Multiply nmol/L by 28.842 — the molar mass divided by ten. So 12 nmol/L is 346 ng/dL, 20 nmol/L is 577 ng/dL, and 30 nmol/L is 865 ng/dL. Note that this is not the reciprocal of the printed 0.0347, which would give 28.82; converting out and back with the two printed factors leaves you about 0.37 ng/dL adrift on a 500 ng/dL result.

Is free testosterone measured in pg/mL or ng/dL?

Both, depending on the laboratory, and the same result looks ten times bigger in one than the other: 1 ng/dL of free testosterone is 10 pg/mL. A free testosterone of 6.5 ng/dL and one of 65 pg/mL are the identical measurement. In SI the unit is pmol/L, not nmol/L, and 65 pg/mL is 225 pmol/L. If your report gives a bare number with no unit, the converter above will read it as each in turn.

Why does my report give free testosterone as a percentage?

Some assays report the free fraction rather than a concentration — typically between 1% and 3% of total in men. A percentage cannot be converted to pg/mL or nmol/L without your total testosterone, which is why this converter asks for it instead of assuming one. Worked through: 2% of a total of 600 ng/dL is 12 ng/dL of free testosterone, which is 120 pg/mL and 416 pmol/L.

What is ng/mL, and why is my result in it?

Nanograms per millilitre appears on some analyser printouts and in most research and veterinary work. It is 100 times larger than ng/dL because a decilitre is 100 millilitres, so 5 ng/mL is 500 ng/dL and 8.5 ng/mL is 850 ng/dL. No molar mass is involved — it is purely a decimal shift, which is why it is the one testosterone conversion that is exact to as many places as you care to write.

Does the conversion depend on which assay my laboratory used?

No. Converting units is arithmetic on a molar mass and is identical for every assay. What does vary between assays is the measurement itself, and by far more than any rounding in the factor: Travison and colleagues, harmonizing four cohort studies, concluded that "a substantial proportion of intercohort variation in testosterone levels is due to assay differences". Two laboratories can disagree by tens of ng/dL on one blood sample. That is the number worth asking about, not the seventh decimal place of 0.0347.

What is a normal testosterone level in nmol/L?

The harmonized range from Travison 2017 is 264–916 ng/dL for healthy non-obese men aged 19–39, which converts to 9.2–31.8 nmol/L with a median of 18.4 nmol/L. Those SI figures are a conversion of the published ng/dL percentiles, not a separately published nmol/L range, and the band covers only men aged 19 to 39 — this page quotes no age-specific range of its own. Your own laboratory's range, which reflects its own assay, is the one your result should be read against.

Free clinical tool

Testosterone Unit Converter

Total testosterone between ng/dL, nmol/L and ng/mL, and free testosterone between pg/mL, ng/dL, pmol/L and percent — with the full conversion tables below.

Reviewed by: Alpha Health Finder Editorial Team
Last reviewed: September 2026

Where the conversion factor comes from

A testosterone result is a mass of hormone in a volume of blood. The United States reports that mass in nanograms per decilitre; the United Kingdom, most of Europe, Australia and Canada report the same blood in nanomoles per litre, which counts molecules instead. Getting from one to the other means dividing by the mass of one mole of testosterone — its molar mass. Nothing else is involved. The conversion is arithmetic, not a calibration, and it does not depend on which laboratory ran the test.

Testosterone is C19H28O2. PubChem (CID 6013) reports its molecular weight to four significant figures as 288.4 g/mol; the value used throughout the endocrine literature, and by this page, is the slightly more precise 288.42 g/mol. The derivation is then one line. One ng/dL is 10 ng/L, which is 1 × 10⁻⁸ g/L; divide by 288.42 g/mol and you get 3.4672 × 10⁻¹¹ mol/L, which is 0.0346717 nmol/L. Round to three significant figures and you have the 0.0347 everybody prints.

Source the molar mass properly, though, and it turns out not to be a single number. NIST publishes standard atomic weights as intervals rather than points, because the isotopic composition of ordinary terrestrial material genuinely varies: carbon is [12.0096, 12.0116], hydrogen [1.00784, 1.00811], oxygen [15.99903, 15.99977]. Run those through C19H28O2 and the molar mass of testosterone is anywhere from 288.400 to 288.447 g/mol. The conversion factor is therefore an interval too — 0.0346684 to 0.0346741 — and the familiar 0.0347 sits just outside the top of it, by 0.075%. That is the honest reason this page will not quote a single "exact" factor beyond the five decimal places the interval supports.

Now the half that matters more. At Travison's median result of 531 ng/dL, every defensible factor lands between 18.409 and 18.426 nmol/L. The entire disagreement is 0.017 nmol/L, which is 0.48 ng/dL — a hundredth of a decimal place on a report that is itself quoted to the nearest whole number. It has never changed a clinical decision and it never will. Use 0.0347 with a clear conscience; the number worth worrying about is the assay, not the arithmetic, and Travison and colleagues found "a substantial proportion of intercohort variation in testosterone levels is due to assay differences".

Free testosterone is where the real confusion lives, and it is not about precision. Laboratories report free testosterone in pg/mL, in ng/dL, as a percentage of total, and in SI as pmol/L — four notations for one quantity, and the report often does not make clear which it used. The concentration units are trivially related (1 ng/dL = 10 pg/mL, and pg/mL × 3.4672 = pmol/L, exactly 100 times the total-testosterone factor because the same molar mass is applied to units a hundredfold apart). The percentage is not: it cannot be turned into a concentration without your total testosterone, and the converter above refuses to guess one.

The formula

TOTAL TESTOSTERONE

nmol/L = ng/dL × 10 / M M = molar mass, 288.42 g/mol

= ng/dL × 0.0346717 (printed as × 0.0347)

ng/dL = nmol/L × M / 10 = nmol/L × 28.842

ng/mL = ng/dL / 100 (a decimal shift, no molar mass)

FREE TESTOSTERONE

ng/dL = pg/mL / 10

pmol/L = pg/mL × 1000 / M = pg/mL × 3.46717 (printed as × 3.47)

pg/mL = (percent / 100) × total ng/dL × 10

M is the only constant in any of this. Every factor above is M rearranged, which is why the free-testosterone factor is exactly 100× the total-testosterone one. The reverse factor is M/10 = 28.842, not 1 / 0.0347 = 28.818 — converting out with the printed factor and back with the printed reciprocal does not return you to where you started.

Worked example

A United States report reading 500 ng/dL, converted for a clinician who works in nmol/L:

Molar-mass factor: 500 × 0.0346717 = 17.336 nmol/L
Printed factor: 500 × 0.0347 = 17.350 nmol/L
The two differ by 0.014 nmol/L, which read back is 0.41 ng/dL out of 500 — 0.082%. A report quoting one decimal place can show 17.3 or 17.4 depending only on which factor the laboratory's software used — the single visible consequence of the rounding anywhere on this page.
Same reading in ng/mL: 500 / 100 = 5.0 ng/mL.
Round trip with the printed pair: 500 × 0.0347 = 17.35, then × 28.84 = 500.37 ng/dL. You are 0.37 ng/dL from where you began, which is where two websites' answers diverge.
Free testosterone on the same man, if his SHBG were 30 nmol/L: the Vermeulen equation gives 10.8 ng/dL, which is the same result as 108 pg/mL, 376 pmol/L, or 2.17% of total. Four numbers, one measurement.

Testosterone conversion chart — ng/dL to nmol/L

Total testosterone across the range laboratories report. Find your ng/dL on the left; the nmol/L figure is what a UK, European, Australian or Canadian report would show for the same blood.

Total T	nmol/Lfrom molar mass	nmol/L× 0.0347	Differencenmol/L	ng/mL
100 ng/dL	3.47	3.47	0.003	1.00
150 ng/dL	5.20	5.21	0.004	1.50
200 ng/dL	6.93	6.94	0.006	2.00
250 ng/dL	8.67	8.68	0.007	2.50
264 ng/dL	9.15	9.16	0.007	2.64
300 ng/dL	10.40	10.41	0.009	3.00
350 ng/dL	12.14	12.15	0.010	3.50
400 ng/dL	13.87	13.88	0.011	4.00
450 ng/dL	15.60	15.62	0.013	4.50
500 ng/dL	17.34	17.35	0.014	5.00
550 ng/dL	19.07	19.09	0.016	5.50
600 ng/dL	20.80	20.82	0.017	6.00
700 ng/dL	24.27	24.29	0.020	7.00
800 ng/dL	27.74	27.76	0.023	8.00
900 ng/dL	31.20	31.23	0.026	9.00
916 ng/dL	31.76	31.79	0.026	9.16
1000 ng/dL	34.67	34.70	0.028	10.00
1200 ng/dL	41.61	41.64	0.034	12.00
1500 ng/dL	52.01	52.05	0.043	15.00

The 264 and 916 ng/dL rows are the 2.5th and 97.5th percentiles of the harmonized reference range (Travison TG, et al. J Clin Endocrinol Metab. 2017;102(4):1161–1173, PMID 28324103; healthy non-obese men 19–39, measured against the CDC reference method), included so the band can be read in either unit. The difference column is what the rounded 0.0347 costs: never as much as 0.04 nmol/L anywhere on this table. Every figure computed by the same function the converter above calls.

Testosterone conversion chart — nmol/L to ng/dL

The other direction, for a report issued in SI units. Multiply nmol/L by the molar mass over ten to get ng/dL.

Total T	ng/dL× 28.842	ng/dL× 28.84	ng/mL
3 nmol/L	86.53	86.52	0.87
5 nmol/L	144.21	144.20	1.44
8 nmol/L	230.74	230.72	2.31
10 nmol/L	288.42	288.40	2.88
12 nmol/L	346.10	346.08	3.46
14 nmol/L	403.79	403.76	4.04
16 nmol/L	461.47	461.44	4.61
18 nmol/L	519.16	519.12	5.19
20 nmol/L	576.84	576.80	5.77
22 nmol/L	634.52	634.48	6.35
25 nmol/L	721.05	721.00	7.21
30 nmol/L	865.26	865.20	8.65
35 nmol/L	1009.47	1009.40	10.09
40 nmol/L	1153.68	1153.60	11.54
45 nmol/L	1297.89	1297.80	12.98
52 nmol/L	1499.78	1499.68	15.00

The reverse factor is the molar mass divided by ten, 28.842 — not the reciprocal of the printed forward factor, which is 28.818. The two columns show what that discrepancy looks like in practice: under a single ng/dL until you are well above the reference range.

Free testosterone conversion chart — pg/mL, ng/dL, pmol/L

The four notations laboratories use for free testosterone, side by side. The percentage column assumes a total testosterone of 600 ng/dL, because a percentage means nothing without one.

Free T	ng/dL	pmol/Lfrom molar mass	pmol/L× 3.47	% of totalat 600 ng/dL
10 pg/mL	1.0	34.7	34.7	0.17%
20 pg/mL	2.0	69.3	69.4	0.33%
30 pg/mL	3.0	104.0	104.1	0.50%
40 pg/mL	4.0	138.7	138.8	0.67%
50 pg/mL	5.0	173.4	173.5	0.83%
65 pg/mL	6.5	225.4	225.6	1.08%
75 pg/mL	7.5	260.0	260.3	1.25%
100 pg/mL	10.0	346.7	347.0	1.67%
125 pg/mL	12.5	433.4	433.8	2.08%
150 pg/mL	15.0	520.1	520.5	2.50%
200 pg/mL	20.0	693.4	694.0	3.33%
250 pg/mL	25.0	866.8	867.5	4.17%
300 pg/mL	30.0	1040.1	1041.0	5.00%

THIS TABLE CARRIES NO REFERENCE RANGE, and that is deliberate. There is no harmonized reference range for calculated free testosterone the way Travison 2017 provides one for total, so no row here is marked normal or low. Read the figure against your own laboratory's stated range. The percentage column is arithmetic on an assumed total of 600 ng/dL — substitute your own in the converter above.

Every route to the conversion factor, compared

The same conversion derived six ways. Four are defensible and agree to four decimal places; one is the rounded figure in common use; one is the wrong quantity entirely.

Route	Molar massg/mol	ng/dL → nmol/L	500 ng/dL givesnmol/L
Lightest permitted molar massLower bound of the NIST standard atomic weights for C, H and O	288.39998	0.0346741	17.337
Heaviest permitted molar massUpper bound of the NIST standard atomic weights for C, H and O	288.44702	0.0346684	17.334
PubChem CID 6013PubChem reports MolecularWeight to four significant figures: 288.4	288.40000	0.0346741	17.337
Clinical conventionThe 288.42 g/mol used throughout the endocrine literature and by this site’s Vermeulen calculator	288.42000	0.0346717	17.336
Printed factorThe 0.0347 printed in journal SI-conversion footnotes and on lab slips	none — it is a rounding	0.0347000	17.350
Monoisotopic massdo not use — see footnote	288.20893	0.0346971	17.349

The first two rows are the bounds NIST's standard atomic weight intervals put on the molar mass of C19H28O2; everything between them is permitted by natural isotopic variation. The printed 0.0347 sits 0.075% above the top of that interval. The last row is a trap worth naming: PubChem's ExactMass, 288.208930132, is the monoisotopic mass — the mass of a single molecule in which every carbon is ¹²C — not a molar mass, and it must not be used to convert a serum concentration. It happens to round to the same three figures as the printed factor, which is a coincidence and not an origin.

The harmonized reference range in both units

Travison 2017 published its percentiles in ng/dL. These are the same percentiles converted — not a separately published nmol/L range.

Percentile	ng/dLas published	nmol/Lfrom molar mass	nmol/L× 0.0347	Gapng/dL equivalent
2.5th	264	9.15	9.16	0.22
5th	303	10.51	10.51	0.25
50th (median)	531	18.41	18.43	0.43
95th	852	29.54	29.56	0.70
97.5th	916	31.76	31.79	0.75

Travison TG, Vesper HW, Orwoll E, et al. J Clin Endocrinol Metab. 2017;102(4):1161–1173 (PMID 28324103). Healthy non-obese men aged 19–39 from four cohorts, with testosterone in 100 participants per cohort "measured using a reference method at Centers for Disease Control and Prevention (CDC)" and the remainder normalised to it. Ranges shift with age and this one does not apply to men outside 19–39. This converter sources only the 19–39 percentiles and states no age-specific range of its own; that is a limit of what is quoted here, not a claim that none exists. The right-hand column is the whole cost of the rounded factor: under a single ng/dL at every boundary in the range.

Frequently asked questions

How do I convert testosterone from ng/dL to nmol/L?: Multiply ng/dL by 0.0347, or divide by 28.84. A total testosterone of 500 ng/dL is 17.34 nmol/L; 300 ng/dL is 10.40 nmol/L; 900 ng/dL is 31.20 nmol/L. The factor is the molar mass of testosterone, 288.42 g/mol, rearranged — nothing about it depends on your laboratory or your assay.
What is 500 ng/dL of testosterone in nmol/L?: 17.34 nmol/L, or 17.35 nmol/L if you use the rounded 0.0347 factor that journals print. Both round to 17.3 nmol/L at the precision a report would state. In ng/mL the same result is 5.0 ng/mL. For context, 500 ng/dL sits just below the 531 ng/dL median of the harmonized reference range for healthy non-obese men aged 19–39.
Is the 0.0347 testosterone conversion factor wrong?: Not wrong, but it is a rounding rather than a measurement, and it is very slightly high. Derived from the molar mass the factor is 0.0346717, and NIST's standard atomic weight intervals put it somewhere between 0.0346684 and 0.0346741 — so 0.0347 sits 0.075% above the top of the permitted range. What that costs at a real result is 0.014 nmol/L on a 500 ng/dL reading, or 0.41 ng/dL read back. It has never changed a clinical decision. Use it.
What is 10 nmol/L of testosterone in ng/dL?: 288.4 ng/dL. Multiply nmol/L by 28.842 — the molar mass divided by ten. So 12 nmol/L is 346 ng/dL, 20 nmol/L is 577 ng/dL, and 30 nmol/L is 865 ng/dL. Note that this is not the reciprocal of the printed 0.0347, which would give 28.82; converting out and back with the two printed factors leaves you about 0.37 ng/dL adrift on a 500 ng/dL result.
Is free testosterone measured in pg/mL or ng/dL?: Both, depending on the laboratory, and the same result looks ten times bigger in one than the other: 1 ng/dL of free testosterone is 10 pg/mL. A free testosterone of 6.5 ng/dL and one of 65 pg/mL are the identical measurement. In SI the unit is pmol/L, not nmol/L, and 65 pg/mL is 225 pmol/L. If your report gives a bare number with no unit, the converter above will read it as each in turn.
Why does my report give free testosterone as a percentage?: Some assays report the free fraction rather than a concentration — typically between 1% and 3% of total in men. A percentage cannot be converted to pg/mL or nmol/L without your total testosterone, which is why this converter asks for it instead of assuming one. Worked through: 2% of a total of 600 ng/dL is 12 ng/dL of free testosterone, which is 120 pg/mL and 416 pmol/L.
What is ng/mL, and why is my result in it?: Nanograms per millilitre appears on some analyser printouts and in most research and veterinary work. It is 100 times larger than ng/dL because a decilitre is 100 millilitres, so 5 ng/mL is 500 ng/dL and 8.5 ng/mL is 850 ng/dL. No molar mass is involved — it is purely a decimal shift, which is why it is the one testosterone conversion that is exact to as many places as you care to write.
Does the conversion depend on which assay my laboratory used?: No. Converting units is arithmetic on a molar mass and is identical for every assay. What does vary between assays is the measurement itself, and by far more than any rounding in the factor: Travison and colleagues, harmonizing four cohort studies, concluded that "a substantial proportion of intercohort variation in testosterone levels is due to assay differences". Two laboratories can disagree by tens of ng/dL on one blood sample. That is the number worth asking about, not the seventh decimal place of 0.0347.
What is a normal testosterone level in nmol/L?: The harmonized range from Travison 2017 is 264–916 ng/dL for healthy non-obese men aged 19–39, which converts to 9.2–31.8 nmol/L with a median of 18.4 nmol/L. Those SI figures are a conversion of the published ng/dL percentiles, not a separately published nmol/L range, and the band covers only men aged 19 to 39 — this page quotes no age-specific range of its own. Your own laboratory's range, which reflects its own assay, is the one your result should be read against.

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Related calculators

Educational reference, not medical advice. Converting units changes the notation and not the result. Nothing on this page interprets a testosterone level, and the modelled free testosterone range used to flag an unlabelled value — 30 to 288 pg/mL, computed by the Vermeulen equation across the harmonized total range at SHBG 15–70 nmol/L — is an arithmetic sanity check, not a reference range and not a normal range. Read your result against your own laboratory's range, with your clinician.