Molar mass of sodium hydroxide (NaOH)

The molar mass of sodium hydroxide (NaOH) is 39.9967693 g/mol, summed from the IUPAC standard atomic weights of Na, O, H.

Mass of sample

Amount of substance

mol

Molar mass

39.996 769 3g/mol

= Exact Molar mass of sodium hydroxide

Moles in the sample mass: 0.250 020 19 mol
Mass of that amount of substance: 39.996 769
Molecules in the sample mass: 1.50566e+23

Show the working

Mass of sample = 10
Amount of substance = 1
Molar mass = 22.98976928 + 15.999 + 1.008 = 39.9968
Moles in the sample mass = 10 / 39.9968 = 0.250 02
Mass of that amount of substance = 1 * 39.9968 = 39.9968
Molecules in the sample mass = 0.250 02 * NA = 1.50566e+23

Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.

Scenarios & local history

Compare a saved scenario

Recent calculations

The formula

Molar mass = sum over elements of (atomic weight x number of atoms)
For NaOH: 22.98976928 + 15.999 + 1.008 = 39.9967693 g/mol
Moles = mass / molar mass; mass = moles x molar mass
Molecules = moles x 6.02214076 x 10^23 (the Avogadro constant, exact by definition)

Molar mass in grams per mole is numerically equal to the molecular mass in daltons, so this figure doubles as the molecular weight.

Atomic weights are the IUPAC 2021 standard values. Several elements have a range rather than a single value because isotope ratios vary between sources; the conventional single value is used here.

Composition by mass

Element	Atoms	Atomic weight	Contribution (g/mol)	Share of mass
Sodium (Na)	1	22.98976928	22.989769	57.479 %
Oxygen (O)	1	15.999	15.999	40.001 %
Hydrogen (H)	1	1.008	1.008	2.5202 %

Contributions add to the molar mass of 39.9967693 g/mol. Atomic weights are the IUPAC 2021 standard values.

Frequently asked

What is the molar mass of sodium hydroxide?

39.9967693 g/mol, for the formula NaOH.

How do you convert grams of sodium hydroxide to moles?

Divide the mass in grams by 39.9967693 g/mol. One gram of sodium hydroxide is 0.025002 mol.

How many grams are in one mole of sodium hydroxide?

39.9967693 g, by definition of the molar mass.

Is molar mass the same as molecular weight?

Numerically yes, for the purposes of this calculation. Molecular weight is a dimensionless ratio and molar mass carries units of g/mol, but the digits are identical.

Where the numbers come from

IUPAC 2021 standard atomic weights; Avogadro constant fixed by the 2019 SI.