Chemistry
Moles from mass
The rearrangement used most often in practice: convert a weighed mass into moles before any stoichiometry can be done.
The Formula
n = m / M
The rearrangement used most often in practice: convert a weighed mass into moles before any stoichiometry can be done.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| m | Mass of the sample | grams | What the balance reads, in grams. |
| M | Molar mass | grams per mole | Looked up or computed from the formula. |
| n | Amount of substance | moles | The moles the sample contains. |
What Each Symbol Means
mgrams
Mass of the sample
What the balance reads, in grams.
Mgrams per mole
Molar mass
Looked up or computed from the formula.
nmoles
Amount of substance
The moles the sample contains.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate molar mass page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Molar Mass, filed under Science. Every number the guide produces comes from substituting into this one line.