Supports parentheses (), brackets [], braces {}, and hydration dots (· or .).
What this molar mass calculator does
This calculator finds the molar mass (also called molecular weight or formula weight) of a compound from its chemical formula. Enter a valid formula and the tool will compute the total mass in g/mol, plus a clean element-by-element breakdown. It is useful for chemistry homework, lab prep, stoichiometry, solution concentration work, and quick checks during reaction balancing.
How to use it
- Type a formula such as H2O, NaCl, or C6H12O6.
- Use parentheses for grouped atoms, such as Ca(OH)2 or (NH4)2SO4.
- Use hydration notation with a dot, such as CuSO4·5H2O.
- Click Calculate Molar Mass (or press Enter in the input field).
The core idea behind molar mass
Molar mass is the sum of each element's atomic mass multiplied by how many atoms of that element appear in the formula:
Molar mass = Σ (atomic mass × atom count)
Example for water, H2O: 2 × (H) + 1 × (O) = 2 × 1.008 + 15.999 = 18.015 g/mol (approximately).
Supported formula patterns
1) Simple formulas
Examples: H2O, CO2, NH3, NaCl
2) Grouped formulas
Examples: Al2(SO4)3, Ca(OH)2, K4[Fe(CN)6]
3) Hydrates
Hydrates can be entered with a middle dot or period. For example: CuSO4·5H2O or CuSO4.5H2O.
Worked examples
- CO2 → about 44.009 g/mol
- Ca(OH)2 → about 74.092 g/mol
- (NH4)2SO4 → about 132.14 g/mol
- CuSO4·5H2O → about 249.68 g/mol
Common input mistakes to avoid
- Incorrect element capitalization (use Na, not NA).
- Unbalanced parentheses/brackets.
- Missing numbers after grouped units where needed.
- Using unsupported characters in the formula field.
FAQ
Is molar mass the same as molecular weight?
In many practical contexts, people use these terms interchangeably. In formal usage, molar mass is expressed in g/mol.
Can I use this for ionic compounds?
Yes. It works for compounds represented by valid chemical formulas, including ionic compounds and many coordination-style formulas.
How precise are the results?
Results are based on standard average atomic masses and shown to four decimal places. For advanced analytical work, always match your required precision to your lab or textbook standards.