What Is Molar Weight?
Molar weight (also called molar mass) is the mass of one mole of a substance, expressed in grams per mole (g/mol). A mole is a counting unit in chemistry equal to approximately 6.022 × 1023 particles. Knowing molar weight helps you convert between grams, moles, and molecules in laboratory work, coursework, and industrial calculations.
How to Use This Molar Weight Calculator
- Type a valid chemical formula in the input field.
- Use standard element symbols with proper capitalization (for example, Na not NA).
- Add subscripts as numbers directly after symbols (H2SO4).
- Use parentheses for grouped atoms (Al2(SO4)3).
- Hydrates are supported with a middle dot, such as CuSO4·5H2O.
After calculation, you’ll get the total molar weight plus a composition table showing each element’s atom count and mass contribution.
Worked Examples
Water (H2O)
Hydrogen contributes 2 × 1.008 g/mol and oxygen contributes 1 × 15.999 g/mol. Total = 18.015 g/mol.
Glucose (C6H12O6)
Carbon, hydrogen, and oxygen contributions are summed from their atomic weights multiplied by subscripts. The result is approximately 180.156 g/mol.
Calcium Hydroxide (Ca(OH)2)
The parentheses mean the OH group appears twice, so both oxygen and hydrogen counts are multiplied by 2.
Copper(II) Sulfate Pentahydrate (CuSO4·5H2O)
The hydrate dot indicates five water molecules added to CuSO4. The calculator handles this by calculating each part and combining them.
Why Accurate Molar Weight Matters
- Stoichiometry: Correct reactant and product quantities depend on precise molar masses.
- Solution prep: Making 0.1 M or 1.0 M solutions requires exact grams per liter.
- Lab reproducibility: Better mass calculations improve repeatability and reduce error.
- Quality control: Manufacturing and analytical chemistry rely on accurate molecular calculations.
Tips for Entering Formulas Correctly
- Use element symbols exactly as defined in the periodic table.
- Do not add spaces inside formulas.
- Double-check parentheses and brackets for balance.
- Use numeric coefficients only where chemically meaningful.
Frequently Asked Questions
Is molar weight the same as molecular weight?
In everyday chemistry use, they are often treated similarly, but molar weight is explicitly mass per mole (g/mol).
Can this tool handle nested parentheses?
Yes. Complex formulas like K4[Fe(CN)6] are supported.
Does it support hydrates?
Yes. Hydrate notation such as “·5H2O” is supported.
Bottom Line
This molar weight calculator is designed to be fast, practical, and useful for students, teachers, and professionals. Enter your chemical formula above to get a reliable molar mass and element-by-element breakdown instantly.