Quickly compute the molecular weight (molar mass) of any compound from its chemical formula. Our Molecular Weight Calculator supports parentheses, brackets, and hydrate notation, delivering accurate results in g/mol with your chosen precision.
What is molecular weight and why it matters
Molecular weight—more precisely, molar mass—is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the average atomic weights of all atoms in the chemical formula. Accurate molar mass values are essential for stoichiometric calculations, preparing solutions, converting between moles and grams, and verifying chemical formulas. Whether you are a student balancing equations, a researcher planning syntheses, or a professional preparing standards, a dependable calculator saves time and reduces errors.
How to use the Molecular Weight Calculator
- Enter the compound’s chemical formula, using correct element symbols and capitalization (e.g., H2O, C6H12O6, Fe2(SO4)3).
- Use parentheses and square brackets for complex ions and grouped units (e.g., K4[Fe(CN)6]).
- For hydrates, use a middle dot: CuSO4·5H2O, CoCl2·6H2O.
- Select your desired decimal places for rounding the final molar mass.
- Click “Calculate Molecular Weight” to see the result and an elemental breakdown.
Supported notation and examples
The calculator recognizes uppercase/lowercase element symbols, integer subscripts, nested parentheses and brackets, and hydrate dots. Examples include:
- Simple compounds: NaCl, H2O, NH3
- Organic molecules: C6H12O6, C12H22O11, CH3COOH
- Inorganic salts: Fe2(SO4)3, Ca(OH)2, Al2O3
- Complex ions and coordination compounds: K4[Fe(CN)6], [Cu(NH3)4]SO4
- Hydrates: CuSO4·5H2O, BaCl2·2H2O
Behind the calculation
Under the hood, the Molecular Weight Calculator parses your formula, counts each element’s atoms (respecting group multipliers), and sums their average atomic weights. Average atomic weights reflect the natural isotopic distribution of elements, which is standard for most lab and classroom work. The result is then rounded to your selected number of decimal places for clear reporting.
Tips for best results
- Use the correct case: “Co” (cobalt) is not the same as “CO” (carbon monoxide).
- Check parentheses and bracket balance; mismatched groupings cause invalid formulas.
- For hydrates, the leading number applies to the water group: “·5H2O” adds five water molecules.
- If an element symbol is not recognized, verify spelling or consult a periodic table.
Why choose this tool
This calculator is designed for accuracy, speed, and clarity. It supports common chemical notations encountered in coursework and research, provides a readable element-by-element contribution list, and lets you control rounding precision. It works well for quick checks, lab prep, and educational demonstrations.
From molar mass to practical chemistry
Once you have the molecular weight, you can convert between grams and moles, set reagent ratios, and estimate yields. For example, knowing that glucose (C6H12O6) has a molar mass of about 180.156 g/mol lets you calculate how many grams are needed for a 0.5 mol solution or how many moles are present in a weighed sample. Accurate molar masses are the first step toward reliable, reproducible chemistry.
Try your own formula now to see instant results.