Calculate mass, molar mass, or moles from the other two values with unit conversions for g, kg, lb, mg, g/mol, kg/mol, and mol, using base units.

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Mass to Moles Formula

The following formula is used to convert mass to moles.

n = m / M

Variables:

  • n is the number of moles (mol)
  • m is the mass of the substance (grams)
  • M is the molar mass of the substance (g/mol)

To convert mass to moles, divide the mass of the substance by its molar mass.

Grams to Moles Conversion Table (Water, M = 18.015 g/mol)
Mass (g) Moles (mol)
0.10.005551
0.250.013877
0.50.027755
10.055509
20.111019
50.277546
100.555093
12.50.693866
150.832639
201.110186
251.387732
502.775465
754.163197
1005.550930
1508.326395
20011.101860
25013.877324
50027.754649
75041.631973
100055.509298
*Assumes substance is water with molar mass M = 18.015 g/mol. Formula: n = m / M.

What is Molar Mass?

Molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol). For routine chemistry, its numerical value in g/mol is approximately the relative molecular or formula mass. Atomic mass units (u) measure particle mass; they are not the same unit as g/mol. The molar mass is used to convert between the mass of a substance and the amount in moles, which is a fundamental concept in chemistry for stoichiometric calculations.

How to Calculate Moles from Mass?

The following steps outline how to calculate the number of moles from mass.

  1. First, determine the mass of the substance (m) in grams.
  2. Next, determine the molar mass of the substance (M) in grams per mole.
  3. Use the formula from above = n = m / M.
  4. Finally, calculate the number of moles (n).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

mass of the substance (m) = 50 grams

molar mass of the substance (M) = 18.015 g/mol (water)