Molar Mass Calculator
Calculate the molar mass of any chemical compound instantly. Enter a molecular formula such as H₂O, NaCl, or C₆H₁₂O₆ and get the precise molecular weight in g/mol with a full element-by-element breakdown.
Molar Mass Calculator
Enter Formula
Use standard notation: H2SO4, Ca(OH)2 (parentheses not yet supported in this simple version).
Enter a chemical formula like H2O or C6H12O6 to calculate its molar mass.
Understanding Molar Mass
Molar mass is one of the most fundamental quantities in chemistry. It represents the mass of exactly one mole of a given substance and is measured in grams per mole (g/mol). One mole contains Avogadro’s number of particles — approximately 6.022 × 1023 atoms, molecules, or formula units — making molar mass the essential link between microscopic atomic masses and macroscopic quantities you can measure on a laboratory balance.
How to Read the Periodic Table
Every element on the periodic table displays an atomic mass (often written below the element symbol). This number, expressed in atomic mass units (amu), is numerically equal to the molar mass of that element in g/mol. For example, carbon (C) has an atomic mass of 12.011 amu, meaning one mole of carbon atoms weighs 12.011 g. Oxygen (O) has an atomic mass of 15.999 amu, so one mole of oxygen atoms weighs 15.999 g.
Calculating Molar Mass for Compounds
To find the molar mass of a compound, add the atomic masses of every atom in its molecular formula. Multiply each element’s atomic mass by the subscript (number of atoms) in the formula, then sum the results. For water (H₂O): (2 × 1.008) + (1 × 16.00) = 18.015 g/mol. For compounds with parentheses, such as Ca(OH)₂, expand first: Ca + 2 O + 2 H, then add the masses.
Avogadro’s Number and the Mole
The mole is defined so that exactly 12 g of carbon-12 contains one mole of atoms. This count — 6.02214076 × 1023 — is called Avogadro’s number (NA). Molar mass lets you convert between grams and moles: divide the mass of your sample by the molar mass to get the number of moles, or multiply moles by molar mass to get grams.
Molar Mass in Stoichiometry
Stoichiometry is the area of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. Balanced equations give ratios in moles. Molar mass converts those mole ratios into gram amounts you can actually weigh, enabling you to determine how much reagent to use, predict theoretical yield, and identify the limiting reagent in a reaction.
Molar Mass of Common Compounds
The table below lists the molar masses of frequently encountered chemical compounds. Use these values as a quick reference or to verify your own calculations.
| Compound | Formula | Molar Mass (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Sodium Chloride (Table Salt) | NaCl | 58.44 |
| Carbon Dioxide | CO₂ | 44.01 |
| Glucose | C₆H₁₂O₆ | 180.16 |
| Ethanol | C₂H₅OH | 46.07 |
| Sulfuric Acid | H₂SO₄ | 98.08 |
| Calcium Carbonate | CaCO₃ | 100.09 |
| Ammonia | NH₃ | 17.03 |
| Hydrochloric Acid | HCl | 36.46 |
| Acetic Acid (Vinegar) | CH₃COOH | 60.05 |
How to Calculate Molar Mass — Worked Examples
Example 1 — Water (H₂O)
- Identify the atoms: 2 hydrogen (H) and 1 oxygen (O).
- Look up atomic masses: H = 1.008 g/mol, O = 16.00 g/mol.
- Multiply and sum: (2 × 1.008) + (1 × 16.00) = 18.015 g/mol.
Example 2 — Sulfuric Acid (H₂SO₄)
- Identify the atoms: 2 H, 1 S, and 4 O.
- Atomic masses: H = 1.008 g/mol, S = 32.07 g/mol, O = 16.00 g/mol.
- Calculate: (2 × 1.008) + (1 × 32.07) + (4 × 16.00) = 2.016 + 32.07 + 64.00 = 98.08 g/mol.
Example 3 — Glucose (C₆H₁₂O₆)
- Identify the atoms: 6 C, 12 H, and 6 O.
- Atomic masses: C = 12.011 g/mol, H = 1.008 g/mol, O = 16.00 g/mol.
- Calculate: (6 × 12.011) + (12 × 1.008) + (6 × 16.00) = 72.066 + 12.096 + 96.00 = 180.16 g/mol.
Glucose is one of the most important biological molecules. Knowing its molar mass allows biochemists to prepare solutions of exact concentration for experiments.
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