⚗️ Molar Mass Calculator
Enter a chemical formula (e.g. H2O, C6H12O6, Ca(OH)2) to get
its molar mass and elemental breakdown.
Counting atoms, then adding standard atomic weights
The formula is parsed into a tally of atoms, and each tally is multiplied by that element's standard atomic weight:
M = Σ (count of element × atomic weight)Glucose, the default C6H12O6, works out as C 12.011 × 6 = 72.066, H 1.008 × 12 = 12.096 and O 15.999 × 6 = 95.994, totalling 180.156 g/mol. Every element's own contribution is listed above the total, which is what you need for percentage composition.
Writing the formula so it parses
- Case is meaningful. A symbol is a capital plus an optional lowercase letter, so CO is carbon monoxide and Co is cobalt.
- A number applies to the symbol before it, and a missing number means one.
- Parentheses multiply everything inside and can be nested: Ca(OH)2 counts two oxygens and two hydrogens.
| Formula | Molar mass |
|---|---|
| H2O | 18.015 g/mol |
| NaCl | 58.440 g/mol |
| Ca(OH)2 | 74.092 g/mol |
| H2SO4 | 98.072 g/mol |
Frequently asked questions
What is the molar mass of glucose?
180.156 g/mol. C6H12O6 holds six carbons at 12.011, twelve hydrogens at 1.008 and six oxygens at 15.999.
What is the difference between CO and Co?
CO is carbon monoxide at 28.010 g/mol; Co is the element cobalt at 58.933 g/mol. The lowercase letter is part of the symbol, not a second element.
How do I enter a hydrate such as copper sulfate pentahydrate?
The centre dot is not accepted, so do the two halves separately. CuSO4 is 159.602 g/mol and five waters add 90.075, giving 249.677 g/mol.