Convert ng/mL to nM, or nM to ng/mL, from the compound’s molecular weight, with pg/mL, µg/mL, mg/L, pM, µM and mM units also available.
| ng/mL to nM | nM to ng/mL |
|---|---|
| 0.1 ng/mL = 0.555 nM | 0.5 nM = 0.0901 ng/mL |
| 0.2 ng/mL = 1.110 nM | 1 nM = 0.1802 ng/mL |
| 0.5 ng/mL = 2.775 nM | 2 nM = 0.3603 ng/mL |
| 1 ng/mL = 5.551 nM | 5 nM = 0.9008 ng/mL |
| 2 ng/mL = 11.10 nM | 10 nM = 1.8016 ng/mL |
| 5 ng/mL = 27.75 nM | 25 nM = 4.504 ng/mL |
| 10 ng/mL = 55.51 nM | 50 nM = 9.008 ng/mL |
| 20 ng/mL = 111.0 nM | 100 nM = 18.016 ng/mL |
| 50 ng/mL = 277.5 nM | 250 nM = 45.04 ng/mL |
| 100 ng/mL = 555.1 nM | 500 nM = 90.08 ng/mL |
| Formulas: nM = (ng/mL x 1000) / MW; ng/mL = (nM x MW) / 1000. MW = 180.16 g/mol. | |
| ng/mL to nM | nM to ng/mL |
|---|---|
| 0.25 ng/mL = 0.5 nM | 0.2 nM = 0.1 ng/mL |
| 0.5 ng/mL = 1 nM | 0.4 nM = 0.2 ng/mL |
| 1 ng/mL = 2 nM | 1 nM = 0.5 ng/mL |
| 2.5 ng/mL = 5 nM | 2 nM = 1 ng/mL |
| 5 ng/mL = 10 nM | 4 nM = 2 ng/mL |
| 10 ng/mL = 20 nM | 10 nM = 5 ng/mL |
| 25 ng/mL = 50 nM | 20 nM = 10 ng/mL |
| 50 ng/mL = 100 nM | 40 nM = 20 ng/mL |
| 100 ng/mL = 200 nM | 100 nM = 50 ng/mL |
| 250 ng/mL = 500 nM | 200 nM = 100 ng/mL |
| Formulas: nM = (ng/mL x 1000) / MW; ng/mL = (nM x MW) / 1000. MW = 500 g/mol. | |
ng/mL to nM Formula
The conversion from nanograms per milliliter to nanomolar relies on the molecular weight (MW) of the analyte:
Where ng/mL is the mass concentration and MW is the molar mass in g/mol. Molecular mass in daltons (Da) and molar mass in g/mol are different quantities with approximately the same numerical value. The factor of 1000 follows from 1 ng/mL = 10-6 g/L and 1 mol/L = 109 nM. To reverse the conversion: ng/mL = (nM x MW) / 1000.
Why Molecular Weight Determines the Conversion
ng/mL is a mass-per-volume unit. nM is a molar unit, counting the number of molecules per liter (specifically, nanomoles per liter). Because different substances weigh different amounts per molecule, two analytes at the same ng/mL can represent vastly different numbers of molecules. For example, 10 ng/mL of cortisol (MW 362.46) equals about 27.6 nM, while 10 ng/mL of insulin (MW 5,808) equals only about 1.72 nM. The heavier the molecule, the fewer nanomoles are present per nanogram.
Where This Conversion Is Used
Therapeutic drug monitoring (TDM), ELISA and LC-MS/MS assays may report concentrations in mass or molar units; use the units and sample type on the actual report. Conversion places a concentration on a molar scale for pharmacokinetic analysis, bioanalytical method development and toxicology research. Comparison with Kd, IC50 or EC50 also requires the correct chemical form, free versus total concentration, relevant sample or target compartment and experimental conditions. Unit conversion alone does not establish clinical efficacy or a safe dose.
Reference Molecular Weights for Common Analytes
The table below gives rounded reference molar masses for the chemical forms named in each row. Match the measured analyte, salt or hydrate basis before using a value. Protein values marked approximate depend on the specified monomer, intact antibody or other construct; use the actual product or construct molar mass for precise conversion.
| Analyte | Category | MW (g/mol) | 1 ng/mL = |
|---|---|---|---|
| Testosterone | Hormone | 288.42 | 3.467 nM |
| Estradiol (E2) | Hormone | 272.38 | 3.671 nM |
| Cortisol | Hormone | 362.46 | 2.759 nM |
| Progesterone | Hormone | 314.46 | 3.180 nM |
| Thyroxine (T4) | Hormone | 776.87 | 1.287 nM |
| 25-Hydroxyvitamin D3 (calcifediol) | Vitamin | 400.64 | 2.496 nM |
| Vitamin B12 (cyanocobalamin) | Vitamin | 1355.37 | 0.738 nM |
| Folic Acid | Vitamin | 441.40 | 2.266 nM |
| Acetaminophen | Drug | 151.16 | 6.616 nM |
| Ibuprofen | Drug | 206.28 | 4.848 nM |
| Metformin (free base) | Drug | 129.16 | 7.742 nM |
| Atorvastatin (free acid) | Drug | 558.64 | 1.790 nM |
| Tacrolimus (anhydrous) | Drug | 804.02 | 1.244 nM |
| Cyclosporine A | Drug | 1202.61 | 0.832 nM |
| Sirolimus | Drug | 914.17 | 1.094 nM |
| Insulin (human) | Protein | 5807.57 | 0.172 nM |
| Human soluble TNF-alpha (monomer; approximate) | Protein | 17,350 | 0.058 nM |
| IgG antibody (intact; approximate) | Protein | 150,000 | 0.0067 nM |
Key Relationships Between Units
nM (nanomolar) is equivalent to nmol/L. The conversion from ng/mL to nmol/L uses the same formula because 1 ng/mL = 1 microgram/L, and dividing micrograms by the molar mass gives micromoles, which then scales to nanomoles by a factor of 1000. Related conversions are: ng/mL to nmol/L (identical to nM); micrograms/mL to micromolar, µM = (micrograms/mL x 1000) / MW; and pg/mL to pM, pM = (pg/mL x 1000) / MW. MW must be in g/mol.
Worked Example
A lab reports a tacrolimus whole-blood trough concentration of 8 ng/mL on an anhydrous mass basis. Using a molar mass of 804.02 g/mol: nM = (8 x 1000) / 804.02 = 9.95 nM. This is a conversion of the total concentration in that sample. Whole-blood tacrolimus includes cell-associated and protein-bound drug and cannot be treated as free target-site concentration or compared directly with an in-vitro binding constant to establish efficacy. Clinical interpretation requires the applicable monitoring protocol and other clinical and laboratory findings.
Common Pitfalls
The most frequent error is inverting the formula, multiplying ng/mL by MW instead of dividing by it. This yields a number with incorrect units. Another mistake is entering a molecular mass in kDa as though it were a molar mass in g/mol: 150 kDa corresponds approximately to 150,000 g/mol, so enter 150,000 when the selected input unit is g/mol. Post-translational modifications such as glycosylation and phosphorylation can change a protein’s mass from its sequence-predicted value. Use the characterized mass of the relevant construct or glycoform; there is no universal percentage correction.
