Universal ng/mL to pmol/L Converter
Universal ng/mL to pmol/L Converter
Convert ng/mL, µg/L, pg/mL, ng/dL and ng/L to pmol/L for any analyte from its molecular weight. For a small peptide the answer is exact. For a glycoprotein there is no single molecular weight to enter, and for a hormone standardised in international units there is no molar conversion at all — which is most of what this page is about.
ng/mL to pmol/L, any analyte
Mass + MW → pmol/LAnti-Müllerian hormone 2.0 ng/mL, molecular weight taken as 140,000 g/mol
The formula, and the assumption inside it
ng/mL = pmol/L × MW ÷ 10⁶
because 1 ng/mL is 10⁻⁶ g/L, and 10⁻⁶ ÷ MW mol/L × 10¹² = (10⁶ ÷ MW) pmol/L
- the derivation
- one nanogram per millilitre is one microgram per litre, which is 1 × 10⁻⁶ grams per litre. Divide by grams per mole for moles per litre; multiply by 10¹² for picomoles. The exponents leave 10⁶
- ÷ MW × 10⁶
- the whole conversion. For anti-Müllerian hormone at an assumed 140,000 g/mol that is 10⁶ ÷ 140 000 = 7.14 pmol/L per ng/mL
- ng/mL = µg/L
- identical. pg/mL and ng/L are also identical to each other, and a thousand times smaller again
- the assumption
- that the measurand has one molecular weight. True for a defined peptide such as insulin, 5808 Da, or C-peptide, 3020 Da. NOT true for a glycoprotein, whose carbohydrate content varies between individuals and between molecules
- what has no molar unit at all
- anything calibrated against a WHO international standard and reported in IU. hCG, LH, FSH, TSH and prolactin are potencies, not masses, and no molecular weight converts them. See the table below
Worked example
Anti-Müllerian hormone 2.0 ng/mL, molecular weight taken as 140,000 g/mol
2.0 ng/mL = 2.0 × 10⁻⁶ g/L
2.0 × 10⁻⁶ ÷ 140 000 = 1.43 × 10⁻¹¹ mol/L = 14.29 pmol/L
The same thing in one step: 2.0 × 7.14 = 14.29, and 7.14 is 10⁶ ÷ 140 000
Now the caveat. UniProt gives AMH a 560-residue precursor of 59,195 Da and describes the active form as a disulfide-linked homodimer, so the dimer's sequence mass is 118,390 Da — which would give 8.45 pmol/L per ng/mL, not 7.14. The difference is the glycosylation, and 140,000 is a convention rather than a measurement
Three kinds of measurand, three different answers
| Kind of measurand | Example | Does a molar conversion work? | Why |
|---|---|---|---|
| A defined peptide | Insulin, 5,808 Da · C-peptide, 3,020 Da | Yes, exactly | The sequence fixes the mass. Every molecule weighs the same |
| A glycoprotein | AMH · thyroglobulin · SHBG · hCG | Only by convention | Carbohydrate is added post-translationally and varies between individuals and between molecules, so there is no single grams-per-mole |
| A heterogeneous or cleaved peptide | AMH again — pro-AMH and cleaved forms circulate together | No | The assay reports several molecular species as one number. There is no one mass to divide by |
| An IU-standardised hormone | hCG · LH · FSH · TSH · prolactin | No, not at all | The result is a potency relative to a WHO reference preparation. It is not a mass and no molecular weight relates it to one |
Hormones with no molar conversion, and what they use instead
| Hormone | Reported as | The calibration | Its own page |
|---|---|---|---|
| Human chorionic gonadotrophin | IU/L, mIU/mL | Potency against a WHO international standard. A heterodimer with variable glycoforms — intact hormone, free β-subunit and nicked forms are detected differently by different assays | hCG converter |
| Luteinising hormone | IU/L, mIU/mL | Potency against a WHO standard. IU/L, mIU/mL and mU/mL are three labels for one number | LH converter |
| Follicle-stimulating hormone | IU/L, mIU/mL | Potency against a WHO standard; no meaningful molar conversion | FSH converter |
| Thyroid-stimulating hormone | mIU/L, µIU/mL, mU/L | Units of biological activity against WHO International Standard 81/565. All three labels are numerically identical | TSH converter |
| Insulin | µIU/mL or pmol/L | The molar step is sound — insulin is 5,808 Da — but the IU step is a potency: 28.8 IU per mg, giving 6.00 pmol/L per µIU/mL | insulin converter |
| Anti-Müllerian hormone | ng/mL or pmol/L | Assays are calibrated by value transfer, some against non-human calibrators. WHO Reference Reagent 16/190 is assigned a MASS potency of 489 ng per ampoule, not an international unit | AMH converter |
Why 140,000 for AMH, and what it costs
| Basis | Mass used | pmol/L per ng/mL | Status |
|---|---|---|---|
| The conventional figure, used by essentially every laboratory and calculator | 140,000 Da | 7.14 | A convention. It is what the site’s own AMH converter uses, so results stay comparable |
| UniProt P03971 precursor, 560 residues | 59,195 Da | 16.89 | Wrong — the circulating active form is a dimer, not a monomer |
| The disulfide-linked homodimer, sequence mass only | 118,390 Da | 8.45 | Arithmetically correct and clinically unused. The 18% gap to 140,000 is the carbohydrate |
The arithmetic is easy; the molecular weight is the hard part
The derivation takes one line. A nanogram per millilitre is a microgram per litre, which is 10⁻⁶ grams per litre; divide by grams per mole for moles per litre; multiply by 10¹² for picomoles. The exponents leave a million, so pmol/L is the ng/mL figure times a million divided by the molecular weight. For a defined peptide that is the end of the matter. Insulin is 5,808 daltons and C-peptide is 3,020, both fixed by their sequences, and the molar conversion for either is exact to as many figures as you care to write.
Peptide and protein hormones are mostly not like that, and this is the page where it has to be said. A glycoprotein’s mass is not set by its gene alone: carbohydrate is attached after translation, at a variable number of sites with variable chain structures, and the result is a population of molecules with a spread of masses rather than a single compound. Anti-Müllerian hormone is the standard illustration because it is the glycoprotein most often converted to molar units. The conventional factor of 7.14 picomoles per litre per nanogram per millilitre comes from an assumed mass of 140,000 daltons. UniProt gives the precursor as 560 residues weighing 59,195 daltons and describes the active hormone as a disulfide-linked homodimer, so the dimer’s sequence mass is 118,390 — which would give 8.45, not 7.14. The eighteen per cent between those two numbers is the sugar, and nobody can tell you how much sugar a particular patient’s AMH is carrying.
It gets one step harder. The collaborative study that established WHO Reference Reagent 16/190 for AMH says in as many words that the molecular mass of AMH is difficult to ascertain, and explains why: each subunit has two potential N-linked glycosylation motifs and possibly O-linked chains, and proteolytic cleavage of the homodimer produces N-terminal and C-terminal dimers that remain non-covalently associated and are measured together as total AMH. So the measurand is not one molecular species at all. The same study found that laboratory estimates of the content of a single ampoule ranged from 282 to 1,157 nanograms, with a geometric coefficient of variation of 42%, which is why the reagent was needed and why serial AMH results must stay on one assay. Use 7.14 because it is the convention and comparability is worth more than false precision; do not represent it as a measured molar mass.
One class of analyte has no molar conversion at all, and offering one would be a category error rather than an inaccuracy. Human chorionic gonadotrophin, luteinising hormone, follicle-stimulating hormone, thyrotrophin and prolactin are reported in international units, and an international unit is a potency defined by comparison with a World Health Organization reference preparation. It is a statement about how much biological activity a sample has relative to an agreed standard, not about how many grams or how many molecules it contains. No molecular weight bridges that, the relationship between IU and mass changes when the standard changes, and each manufacturer establishes its own calibration. If your report is in IU, this page cannot help and the analyte’s own converter will explain what its units do mean.
Frequently asked questions
How do I convert ng/mL to pmol/L?
Multiply by a million and divide by the molecular weight. For anti-Müllerian hormone at the conventional 140,000 g/mol that is 10⁶ ÷ 140,000 = 7.14 pmol/L per ng/mL, so 2.0 ng/mL is 14.3 pmol/L. Going the other way, multiply the pmol/L figure by the molecular weight and divide by a million.
What is the AMH conversion factor from ng/mL to pmol/L?
7.14, so 1 ng/mL is 7.14 pmol/L and 1 pmol/L is 0.14 ng/mL. It follows from an assumed molecular mass of 140,000 daltons. That figure is a convention: the disulfide-linked dimer’s sequence mass is 118,390 daltons, which would give 8.45, and the difference is glycosylation that varies between individuals.
Can I convert hCG, LH or FSH from IU/L to pmol/L?
No. Those results are potencies measured against a WHO international standard, not mass concentrations, so there is no molecular weight to divide by. The relationship between international units and mass changes when the standard changes and differs between manufacturers, which is why no reputable converter offers the step.
Why does a glycoprotein have no single molecular weight?
Because carbohydrate is attached after the protein is made, at a variable number of sites and with variable chain structures, so a glycoprotein circulates as a population of molecules with a range of masses. Any single figure is an average of an assumed population, which is why a molar result for a glycoprotein is nominal.
Is ng/mL the same as µg/L?
Yes, exactly and always — one nanogram in a millilitre is one microgram in a litre. pg/mL and ng/L are likewise identical to each other, and a thousand times smaller. A laboratory switching between either pair has changed nothing about the result.
Should I use this or the analyte’s own converter?
Its own converter wherever one exists, because it also carries the reference interval and, for these analytes, the assay-comparability warning that matters more than the units. This tool is for a peptide with no page of its own, and for checking that a quoted factor is the one its stated molecular weight actually implies.
Related calculators
References
- Ferguson JM, et al. Establishment of a WHO Reference Reagent for anti-Mullerian hormone. Reprod Biol Endocrinol. 2020;18:80. doi:10.1186/s12958-020-00641-9 — reference reagent 16/190, assigned 489 ng/ampoule; laboratory estimates 282–1,157 ng/ampoule, GCV 42%; states that the molecular mass of AMH is difficult to ascertain.
- UniProt Consortium. UniProtKB P03971 (anti-Müllerian hormone): 560 residues, 59,195 Da, homodimer, disulfide-linked, two N-glycosylation sites per subunit.
- UniProt Consortium. UniProtKB P01308 (insulin) — the 5,808 Da mature peptide and the 31-residue C-peptide behind the exact molar conversions quoted here.
- World Health Organization / NIBSC. International Standards and Reference Reagents for pituitary and placental hormones, including TSH IS 81/565, prolactin 3rd IS 84/500 and MIS/AMH Reference Reagent 16/190.
- Bureau International des Poids et Mesures. The International System of Units (SI Brochure). 9th ed. — SI prefixes and the definition of the mole.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.