Molar Mass Calculator — Find the Molecular Weight of Any Compound

Every chemistry calculation eventually comes back to molar mass. Whether you're figuring out how many grams of NaCl to dissolve, converting between moles and grams, or checking stoichiometry, you need the molecular weight first. The CalcHub Molar Mass Calculator takes a chemical formula and spits out the answer in seconds — no periodic table hunting required.

How It Works

Type in a chemical formula (H2O, C6H12O6, Ca(OH)2) and the calculator looks up the atomic mass of each element, multiplies by the subscript, and sums everything up. The result is the molar mass in grams per mole (g/mol).

Compound	Formula	Molar Mass (g/mol)
Water	H₂O	18.015
Table salt	NaCl	58.44
Glucose	C₆H₁₂O₆	180.16
Calcium hydroxide	Ca(OH)₂	74.09
Sulfuric acid	H₂SO₄	98.08

How to Use It

1. Go to CalcHub and open the Molar Mass Calculator.
2. Type the chemical formula using standard notation — capital letters for elements, numbers for subscripts.
3. For compounds with parentheses like Ca(OH)₂, use the same notation you'd write on paper.
4. The tool displays the total molar mass and shows the contribution of each element.

The element breakdown is genuinely useful when you're doing stoichiometry — you can see at a glance that glucose's oxygen atoms contribute 96 g/mol out of its total 180.

The Formula Behind the Calculation

Molar mass is just the sum of (atomic mass × count) for every atom in the formula:

M = Σ (Aᵢ × nᵢ)

For H₂SO₄:

• H: 1.008 × 2 = 2.016


• S: 32.065 × 1 = 32.065


• O: 15.999 × 4 = 63.996


• Total: 98.077 g/mol

Practical Example

You need to prepare 250 mL of a 0.5 M glucose solution. How many grams of glucose do you need?

Moles needed = 0.5 mol/L × 0.250 L = 0.125 mol
Grams = 0.125 mol × 180.16 g/mol = 22.52 g

That's the kind of quick lab prep calculation where having the molar mass at your fingertips saves real time.

Tips

• Capitalization matters: CO is carbon monoxide, Co is cobalt. Get it wrong and you'll get a wildly different mass.
• Hydrates: For compounds like CuSO₄·5H₂O, calculate CuSO₄ and 5×H₂O separately, then add.
• Isotopes: The calculator uses standard atomic weights (natural abundance averages), which is correct for most lab work.

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What's the difference between molar mass and molecular mass?

Molecular mass is measured in atomic mass units (amu) for a single molecule. Molar mass is measured in g/mol and represents the mass of one mole (6.022 × 10²³ molecules). Numerically they're the same — water is 18.015 amu per molecule and 18.015 g/mol — but the context and units differ.

Can I use this for ionic compounds like NaCl?

Yes. For ionic compounds, what you're calculating is technically the formula mass rather than molecular mass (since they don't exist as discrete molecules), but the arithmetic is identical and the result is still called molar mass in practice.

How accurate are the atomic masses used?

The calculator uses IUPAC standard atomic weights, which are the same values you'd find on a modern periodic table. For most lab calculations these are accurate to 4 significant figures.

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Related calculators: Molarity Calculator · Stoichiometry Calculator · Percent Composition Calculator