Molecular Weight Calculator
Calculate Molar Mass
Result
| Molar Mass (Molecular Weight) | — |
|---|
Element Breakdown
| Element | Count | Mass Contribution | % of Total Mass |
|---|---|---|---|
| Enter a formula to see breakdown | |||
How to Use This Molecular Weight Calculator
Typing H2O is easy; typing Ca(OH)2 without miscounting atoms is where chemistry homework gets tedious. Capitalization matters—Co is cobalt, CO is carbon monoxide. This calculator parses chemical formulas including parentheses and subscripts, then returns molar mass in g/mol plus an element-by-element breakdown.
- Enter Chemical Formula. Type a formula like H2SO4, Ca(OH)2, or C6H12O6 using standard notation (case-sensitive).
- Press Calculate Weight. Read Molar Mass (Molecular Weight) in g/mol from the result table.
- Review Element Breakdown. Check each element's count, mass contribution, and percent of total mass below the main result.
Feed the molar mass directly into the Molarity Calculator for solution prep. For density-based mass estimates, see the Density Calculator.
Molecular Weight Calculator Formulas and Practical Applications
Molar mass is the weighted sum of atomic masses for every atom in the formula.
MW = Σ (Atom Count × Atomic Weight)
For Ca(OH)2: one calcium, two oxygens, and two hydrogens (the subscript outside parentheses doubles everything inside). MW ≈ 40.08 + 2(16.00) + 2(1.01) = 74.09 g/mol. Mass percentage helps identify unknown compounds: if analysis shows 40% calcium by mass in a sample, Ca(OH)2 is a reasonable candidate to cross-check against the breakdown table.
Standard Notation Reference
- Subscripts: H2O = two hydrogens, one oxygen
- Parentheses: Mg(OH)2 = Mg + 2 O + 2 H
- Case: NaCl valid; nacl or NACL rejected or misread
- No coefficient prefix: Enter empirical/molecular formula only (e.g., C6H12O6, not 2C6H12O6)
Frequently Asked Questions
Why does capitalization matter in formulas?
Element symbols use a capital first letter followed by an optional lowercase second letter. Co is cobalt (atomic number 27); CO is carbon plus oxygen—carbon monoxide. The parser treats them as completely different compounds.
Can I use parentheses and nested groups?
Yes. Subscripts after parentheses multiply all atoms inside—Mg(OH)2 has one magnesium and two each of oxygen and hydrogen. Mismatched parentheses trigger a validation error.
Which atomic weights does the calculator use?
Standard IUPAC average atomic weights for elements H through Og. For precision isotope work or mass spectrometry, use isotope-specific weights from your instrument or reference table.
What appears in the Element Breakdown table?
Each element's symbol, atom count, mass contribution in g/mol, and percentage of total molar mass—useful for verifying empirical formulas.
How do I use the result for solution prep?
Copy the Molar Mass value into the Formula Weight field of the Molarity Calculator to compute how many grams to dissolve for a target concentration and volume.