Molar Concentration Converter
Molar concentration, or molarity, is the number of moles of a dissolved substance per litre of solution. It is the standard unit of concentration in chemistry and molecular biology because reactions scale with moles. In practice, concentrations span many orders of magnitude, so chemists use SI prefixes: millimolar, micromolar, nanomolar and picomolar. This converter changes a concentration between molar (M), millimolar (mM), micromolar (µM), nanomolar (nM) and picomolar (pM) using exact powers of ten. Enter a value, pick its unit, and read every other unit at once.
Molar concentration conversion formula
value in M = input value * factor of input unit
1 mM = 1e-3 M, 1 µM = 1e-6 M, 1 nM = 1e-9 M, 1 pM = 1e-12 M
value in target unit = value in M / factor of target unit
Each prefix is a fixed power of ten relative to the molar. The converter normalises your input to molar, then expresses it in every other prefix by dividing by the relevant factor.
Worked example
Convert 5 µM to nanomolar. In molar: 5 * 1e-6 = 5e-6 M. In nanomolar: divide by 1e-9, giving 5,000 nM. So 5 µM equals 5,000 nM, a common conversion when reporting enzyme assay concentrations.
Molar concentration: frequently asked questions
What does molar concentration mean?
Molar concentration, also called molarity, is the amount of a dissolved substance per unit volume of solution, expressed in moles per litre. The mole is the SI base unit for amount of substance. A one molar (1 M) solution contains one mole of solute in one litre of solution. Molarity is the most common way to express concentration in chemistry and molecular biology because chemical reactions occur in proportion to moles, not mass.
How do the SI prefixes relate to molar?
Each prefix is a power of ten relative to molar (mol/L). One millimolar (1 mM) is one thousandth of a molar (1e-3 M). One micromolar (1 µM) is one millionth (1e-6 M). One nanomolar (1 nM) is one billionth (1e-9 M). One picomolar (1 pM) is one trillionth (1e-12 M). To convert, multiply or divide by the appropriate power of ten. This converter handles all of these automatically.
When are smaller concentration units used?
Micromolar, nanomolar and picomolar concentrations are common in biochemistry and pharmacology. Enzyme substrates and drug binding constants are often quoted in micromolar or nanomolar. Hormone levels in blood and the affinity of antibodies can reach picomolar. Using the appropriate prefix keeps the numbers readable, for example 5 nM is clearer than 0.000000005 M.
Is molarity the same as molality?
No. Molarity is moles of solute per litre of solution (volume based), while molality is moles of solute per kilogram of solvent (mass based). Molarity changes slightly with temperature because volume expands, whereas molality does not. This converter handles molarity (mol/L) and its SI prefix multiples only. For molality you need the solvent mass rather than the solution volume.
Official sources
- National Institute of Standards and Technology: Guide for the Use of the International System of Units (SI), Special Publication 811.
- National Institute of Standards and Technology: SI prefixes.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.