Enter a concentration in ng/mL (or related mass-per-volume unit) and the molecular weight of your analyte to convert to nanomolar (nM). The calculator solves for any missing variable when two of the three fields are provided.
| 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 = 5.550 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 = 55.50 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 = 555.0 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:
nM = (ng/mL x 1000) / MW
Where ng/mL is the mass concentration, MW is the molecular weight in g/mol (also called daltons), and 1000 is the unit-scaling factor that bridges nanograms to micrograms and milliliters to liters simultaneously. 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) labs report plasma drug levels in ng/mL, but pharmacologists compare those levels against receptor binding affinities expressed in nM. Converting between the two determines whether a measured blood concentration actually reaches the target needed for efficacy. ELISA and LC-MS/MS assays in clinical and research labs also report in ng/mL by default, while IC50 and EC50 values from dose-response curves are expressed in nM, making this conversion a routine step in pharmacokinetic analysis, bioanalytical method development, and toxicology screening.
Reference Molecular Weights for Common Analytes
The table below lists molecular weights for substances frequently measured in ng/mL that need nM conversion. Use these values directly in the calculator above.
| 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 D | Vitamin | 400.64 | 2.496 nM |
| Vitamin B12 | Vitamin | 1355.37 | 0.738 nM |
| Folic Acid | Vitamin | 441.40 | 2.265 nM |
| Acetaminophen | Drug | 151.16 | 6.615 nM |
| Ibuprofen | Drug | 206.28 | 4.848 nM |
| Metformin | Drug | 129.16 | 7.742 nM |
| Atorvastatin | Drug | 558.64 | 1.790 nM |
| Tacrolimus | Drug | 804.02 | 1.244 nM |
| Cyclosporine | Drug | 1202.61 | 0.832 nM |
| Sirolimus | Drug | 914.17 | 1.094 nM |
| Insulin (human) | Protein | 5807.57 | 0.172 nM |
| TNF-alpha | Protein | 17,350 | 0.058 nM |
| IgG antibody | 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 molecular weight gives micromoles, which then scales to nanomoles by the factor of 1000. Related conversions that use the same core relationship: ng/mL to nmol/L (identical result to nM), mcg/mL to micromolar (divide mcg/mL by MW), and pg/mL to pM (same formula, just shifted three orders of magnitude down).
Worked Example
A lab reports a tacrolimus trough level of 8 ng/mL. Tacrolimus has a molecular weight of 804.02 g/mol. Applying the formula: nM = (8 x 1000) / 804.02 = 9.95 nM. This trough concentration can then be compared against in-vitro binding data (tacrolimus binds FKBP12 with a Kd near 0.2 nM), confirming that typical therapeutic blood levels far exceed the binding constant for its primary target.
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 common mistake is using kDa (kilodaltons) directly as the MW without converting to g/mol first; 1 kDa = 1000 g/mol, so an antibody listed at 150 kDa should be entered as 150,000 g/mol. For proteins with post-translational modifications (glycosylation, phosphorylation), the effective MW in solution may differ from the sequence-predicted MW, which can shift the converted value by 5-15% for heavily glycosylated proteins.
