Molar mass calculator
Find the molar mass, element-by-element composition and moles of a chemical formula.
A clear answer. Here’s how.
Reads the formula into element counts, expanding brackets such as Ca(OH)2 and hydrate dots such as CuSO4·5H2O, then adds count × standard atomic weight for each element. Mass percent is each element’s subtotal ÷ the molar mass. Moles = sample mass ÷ molar mass and the particle count uses the exact Avogadro constant. Atomic weights are conventional IUPAC values for elements 1–92, rounded to classroom precision; an optional trailing charge such as ^2- is ignored.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Chemical formula
- Ca(OH)2
- Sample mass (g), to convert to moles
- 10
Example result
| Element | Atoms | Atomic weight (g/mol) | Subtotal (g/mol) | Mass percent |
|---|---|---|---|---|
| Ca (Calcium) | 1 | 40.078 | 40.078 | 54.092% |
| O (Oxygen) | 2 | 15.999 | 31.998 | 43.187% |
| H (Hydrogen) | 2 | 1.008 | 2.016 | 2.721% |
| Total | 5 | 74.092 | 100% |
10 g is 0.134967 mol, about 8.1279e+22 formula units (Avogadro constant 6.02214076×10²³ per mole). Weights are conventional IUPAC values, rounded for classroom use.