Molar to Micromolar Converter
Common Conversions
| M | µM |
|---|---|
| 1e-7 | 0.1 |
| 0.000001 | 1 |
| 0.00001 | 10 |
| 0.0001 | 100 |
| 0.001 | 1000 |
| 0.01 | 10000 |
| 0.1 | 100000 |
| 0.5 | 500000 |
| 1 | 1000000 |
| 2 | 2000000 |
| 5 | 5000000 |
Why this conversion matters in chemistry
Stocks live in molar; assays live in micromolar. The conversion bridges six orders of magnitude in a single step. A 10⁻⁷ M working concentration in a kinase inhibition assay is 0.1 µM — the kind of value that anchors a dose-response curve from a 100 µM top-dose down through three-fold serial dilutions. Multiplying by 10⁶ is the bookkeeping that lets a stock dilution scheme line up with the µM concentrations a screening hit gets reported in. Getting the prefix right is what separates a confident potency comparison from one off by three orders of magnitude.
Formula
Where the factor comes from
Six decimal places separate the two, and the prefix table fixes them exactly — micro is a defined multiplier of 10⁻⁶, so a molar figure becomes micromolar by shifting the point and nothing measured enters. The identity worth carrying away is what those six places do to working volumes. A milliliter is 10⁻³ L and a microliter 10⁻⁶ L, so 1 µM is simultaneously 1 µmol/L, 1 nmol/mL and 1 pmol/µL — three statements of one exact relation, each already scaled to a volume somebody dispenses. Assay work happens in microliters, and the last form answers the question directly: 20 µL of a 5 µM solution delivers 100 pmol. Reaching for the factor of 10⁶ and then converting the volume separately arrives at the same place with more chances to drop a decade.
Precision and significant figures
The factor being exact, the digits are entirely the input's, and the input is usually softer than it looks. Micromolar concentrations of proteins and nucleic acids most often come from absorbance through the Beer–Lambert law, which makes the answer only as good as the extinction coefficient — values computed from sequence are generally quoted as good to within a few percent, and that alone caps the result at two or three significant figures before path length and baseline are considered. Absorbance-based nucleic acid quantitation is looser again, since the conventional mass factors assume a base composition. Reporting 12.47 µM off an A280 reading claims a fourth digit the coefficient never supplied.
Worked Examples
One millimolar in µM — the bridge step between adjacent prefixes most calculations actually take.
One micromolar — a respectable potency for an early-discovery inhibitor.
A typical screening-assay starting concentration, the top of a dose-response titration.
One molar in µM — useful only as a sanity check on the million-fold scale separation.
Common mistakes
The micro sign typed as u or m
Fields that reject non-ASCII characters turn µM into uM, which is harmless, and hurried entry turns it into mM, which is a thousand-fold error in the direction that looks entirely plausible on a screening plate. Anything transcribed between a notebook, an instrument export and a spreadsheet deserves a prefix check at each boundary rather than one at the end of the chain.
Nominal micromolar exceeds aqueous solubility
A compound held at 10 mM in DMSO and diluted a thousand-fold into buffer is nominally 10 µM, but plenty of small molecules come out of solution well below that once the organic co-solvent falls to a tenth of a percent. The well then holds less than the label says, and dose-response curves flatten at the top for reasons having nothing to do with the target.
Milligrams per milliliter is not micromolar
Protein stocks are quoted by mass: a 1 mg/mL antibody near 150 kDa is 6.7 µM, and the molar mass doing that work is itself uncertain, since glycosylation adds mass that varies between lots and between expression systems. A micromolar figure for a large biomolecule is a derived quantity resting on a soft divisor, not a concentration anyone prepared directly.