Micromolar to Nanomolar Converter
Common Conversions
| µM | nM |
|---|---|
| 0.0001 | 0.1 |
| 0.0005 | 0.5 |
| 0.001 | 1 |
| 0.005 | 5 |
| 0.01 | 10 |
| 0.05 | 50 |
| 0.1 | 100 |
| 0.25 | 250 |
| 0.5 | 500 |
| 1 | 1000 |
| 5 | 5000 |
| 10 | 10000 |
Why this conversion matters in chemistry
Going from µM to nM is almost always a potency comparison in disguise. You have a working concentration in µM — the thing you added to the plate — and a published binding constant in nM — the thing you're comparing against. Multiplying the working concentration by 1000 to land in nM is how you answer the practical question: is this dose 10× my Kd, 100×, or off by three orders of magnitude? A 1 µM dose against a 5 nM binder means you're 200-fold over Kd, which is usually saturating. The arithmetic is the easy part. The translation matters more.
Formula
Where the factor comes from
Write both units out in full and the volume disappears. Micromolar is 10⁻⁶ mol/L and nanomolar is 10⁻⁹ mol/L, so the liter sits on both sides of the ratio and cancels, leaving 10⁻⁶ ÷ 10⁻⁹ = 10³. Nothing about the solute enters — not its molar mass, not its charge, not whether it dissociates — because neither unit references the identity of what is dissolved. The factor of 1000 is exact, fixed by the definitions of the two SI prefixes rather than by any measurement, and it would still be exact had the mole never been redefined. One rearrangement is worth carrying in your head: since a liter is 1000 mL, 1 µM equals 1 nmol/mL exactly, and equivalently 1 pmol/µL. That form takes a well volume straight to an amount without a second conversion.
Precision and significant figures
An exact factor adds no uncertainty, so the digits in the nanomolar answer are the digits that were already in the micromolar figure. 0.25 µM is 250 nM — two significant figures in, two out, with the trailing zero doing placeholder duty. The real limit sits upstream. A working concentration reached by serial dilution carries the compounded error of every transfer; three steps at 2% each land near 3.5% overall, a wider band than the tidy converted number implies. Published Kᵢ and IC50 values in nM rarely justify more than two figures either, since curve fitting across a ten-point titration is doing most of the work. Reporting 437.2 nM from a 0.4372 µM entry is arithmetic dressed as measurement.
Worked Examples
A mid-range Ki written two different ways. Whichever unit a paper uses tends to reflect the author's native field as much as anything.
A tight binder. At this affinity most of the compound sits on the target rather than floating around in the buffer.
Common top dose on a screening plate — weak enough that a hit isn't guaranteed, strong enough that a real binder should show up.
Roughly the working concentration for a lot of hormones and growth factors in cell culture — active, but not so much that you're fighting receptor saturation.
Common mistakes
Reading nmol/mL as nanomolar
Peptide and oligonucleotide stocks get quoted in nmol/mL as often as in molar units, and the two read alike at a glance. A stock at 5 nmol/mL is 5 µM, which this page turns into 5000 nM. Taken as 5 nM it sets the working concentration a thousandfold low, and in a binding assay that usually presents as a compound with no activity rather than as a units error.
Matching units does not make IC50s comparable
Putting a screening dose and a literature IC50 into the same unit makes them look directly comparable, and an IC50 is not a fixed property of the compound — it shifts with the substrate or ligand concentration of the assay that produced it. Two groups reporting 40 nM and 400 nM for one inhibitor can both be right. The prefix conversion tidies the notation and leaves that entirely alone.
Working in exponents and losing a step
Expressed in molar terms the exponent drops from 10⁻⁶ to 10⁻⁹ while the coefficient climbs by a thousand, and the two moves have to happen together. Swapping the prefix label alone is where the errors start. 2 µM is 2 × 10⁻⁶ M, which is 2000 nM; writing it as 2 × 10⁻⁹ M keeps the coefficient and takes the exponent shift for free, landing a thousandfold low.