Sodium chloride (NaCl): formula and molar mass
Table salt is sodium chloride, formula NaCl, with a molar mass of 58.44 g/mol. One sodium ion for every chloride ion — though not in molecules, which is the part most pages skip.
Updated on October 7, 2026
Formula, molar mass and composition
NaCl
58.44 g/mol± 0.010
- Formula
- NaCl
- IUPAC
- sodium chloride
- Name
- table salt
- Molar mass
- 58.44 g/mol
Composition by mass
| Symbol | Name | Atoms | Standard atomic weight | Share of mass |
|---|---|---|---|---|
| Na | Sodium | 1 | 22.990 | 39.34 % |
| Cl | Chlorine | 1 | 35.450 | 60.66 % |
IUPAC publishes a range for this element because its isotopic composition varies in nature. The value shown is the conventional atomic weight, and the uncertainty is half the width of that range, not a measurement error.
NaCl is a ratio, not a molecule
Solid salt is an ionic crystal: sodium and chloride ions alternate in a cubic lattice, each surrounded by six of the other kind, with no pairs that you could call a molecule. So NaCl is a formula unit — it states the ratio — and the 58.44 g/mol is strictly a formula mass. Chemists still call it molar mass, which is fine, as long as you do not picture an "NaCl molecule".
Because chlorine is one of the elements whose atomic weight IUPAC publishes as a range, the third decimal of 58.44 depends slightly on where your sample came from. For any school or kitchen purpose, 58.44 g/mol is the number: a level teaspoon of salt, about 6 g, is close to a tenth of a mole.
How to read this page
How to read the numbers here
Every value on "Sodium chloride (NaCl): formula and molar mass" comes from the source named beside its section, never from an estimate of our own with no origin.
Where the data comes from
Each section of "Sodium chloride (NaCl): formula and molar mass" names its official source; the verification date sits at the top of the page.
What the number doesn’t tell you
NaCl’s molar mass shifts slightly with where the sample comes from, because one of its elements has an atomic weight published as a range, not a single value.
More about “Sodium chloride (NaCl): formula and molar mass”
NaCl compared with water
At 58.44 g/mol, one molecule (or formula unit) of NaCl weighs 3.24 times as much as one water molecule. A single gram of NaCl holds roughly 1.0305 × 10²² units — a number that only makes sense because the mole exists.
Worth repeating, because "Sodium chloride (NaCl): formula and molar mass" depends on it: one element in NaCl has an atomic weight published as a range by the IUPAC, so the third decimal place of the molar mass shifts a little with where the sample came from.
Words on this page
Atomic weight
The average weight of an element’s atoms, weighted by how abundant each isotope is in nature, in atomic mass units. For 14 elements CIAAW publishes a range instead of a single value, because that abundance varies a little from sample to sample.
Standard definition by CIAAW — Commission on Isotopic Abundances and Atomic Weights · Atomic weight
Mole
The SI counting unit for atoms, molecules or other entities: one mole is exactly 6.02214076 × 10²³ of them, by the definition fixed in 2019. It is what ties a mass in grams to a number of particles.
Standard definition by BIPM — Bureau International des Poids et Mesures (SI) · Mole
Standard uncertainty
The margin attached to a measured value, usually written in parentheses on the last digits. A constant that is "exact by definition" has zero standard uncertainty; a measured one, like the gravitational constant G, always carries some.
Standard definition by BIPM — Bureau International des Poids et Mesures (SI) · Standard uncertainty
Isotope
Atoms of the same element (same number of protons) with a different number of neutrons, and therefore a different mass. Carbon-12 and carbon-14 are isotopes of carbon; only the second one is radioactive.
Atomic number
The number of protons in an atom’s nucleus, written Z. It is this number, not the mass, that defines which element an atom is: every atom with 8 protons is oxygen, whether it has 8 or 18 neutrons.
Standard definition by IUPAC · Atomic number