Molar to Nanomolar Converter
Common Conversions
| M | nM |
|---|---|
| 1e-9 | 1 |
| 1e-8 | 10 |
| 1e-7 | 100 |
| 0.000001 | 1000 |
| 0.00001 | 10000 |
| 0.0001 | 100000 |
| 0.001 | 1000000 |
| 0.01 | 10000000 |
| 0.1 | 100000000 |
| 1 | 1000000000 |
| 10 | 10000000000 |
| 100 | 100000000000 |
Why this conversion matters in chemistry
Stock bottles sit at M or mM; the assay well sits at nM. A 10 mM inhibitor in DMSO is 10⁷ nM, and walking that down to a 10 nM final concentration is a million-fold dilution — no single step does it, which is why serial dilutions exist. Multiplying by 10⁹ is the factor that lives behind those dilution schemes. It's also the reason a low-nanomolar IC50 is something to get excited about: a compound that works at 1 nM has to reach its target at roughly one part in 10⁹ compared to a stock that was itself already a considered dilution.
Formula
Where the factor comes from
Nano is a fixed multiplier of 10⁻⁹ and the liter is exactly a cubic decimeter, so the factor is exact and nothing measured enters it. More useful than that reassurance is what the exactness lets you compute. Since 2019 the Avogadro constant has been fixed at exactly 6.02214076 × 10²³ per mole, so 1 nM is by definition 6.02214076 × 10¹⁴ molecules per liter — exact as a relation between the numbers, though no real solution is ever exactly 1 nM. Scaled to volumes people actually handle, that is roughly 600 molecules in a picoliter droplet and six hundred thousand in a nanoliter. Nanomolar is where a concentration starts to be worth reading as a headcount, and this factor is what gets you there.
Precision and significant figures
An exact factor of a billion cannot rescue what the nanomolar figure was built from. Most values reported in nM are not direct measurements but parameters fitted to a curve — a Kd or an IC50 emerging from nonlinear regression over eight or ten points, with a confidence interval frequently approaching two-fold and rarely quoted alongside it. Two significant figures flatters most of them. A physical limit sits under the statistical one: nanomolar solutions lose an appreciable fraction of their solute to tube walls, pipette tips and filter membranes, so the concentration in the well is below the one calculated from the dilution scheme. The conversion reports the nominal value and knows nothing of either effect.
Worked Examples
A 1 M stock expressed in nM — the sort of number that makes the billion-fold dilution feel real.
The definition itself. A 1 nM working concentration is at the tight end of what most biochemical assays can detect.
One millimolar written in nM — a DMSO stock concentration, a million-fold above the well.
One micromolar. Below this, you're usually in single-digit nM territory only if the compound is potent.
Common mistakes
Adsorption drains a nanomolar solution
At 1 nM a peptide or a hydrophobic small molecule can lose a large share of its mass to polypropylene before the plate is ever read, and the loss worsens in low-volume formats where the surface-to-volume ratio climbs. The calculated concentration is an upper bound. Carrier protein or detergent is the usual remedy; the arithmetic reports the value you intended, not the one in the well.
Dilution errors compound rather than average
Reaching 10 nM from a 10 mM stock is a million-fold step, done as three or four transfers because no single one is trustworthy over that range. Each transfer carries its own volumetric error and they add in quadrature, so four steps at two percent apiece land near four percent overall. The final nanomolar figure inherits that, however exactly the 10⁹ was applied.
Added ligand is not free ligand
When a binding partner is present at a concentration comparable to the dissociation constant — routine once Kd falls into the low nanomolar range — a substantial fraction of the ligand is bound, and the free concentration driving the equilibrium sits below the nominal one. Fitting such data with the simple isotherm returns a Kd that tracks the receptor concentration rather than the affinity.