Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a chemical formula. Molar mass is essential in chemistry for stoichiometric calculations, preparing solutions, determining empirical formulas, and converting between mass and moles. For example, the molar mass of water (H₂O) is approximately 18.015 g/mol (2 × 1.008 for hydrogen + 15.999 for oxygen).

Use parentheses () or square brackets [] for groups of atoms, followed by a subscript number indicating how many times the group repeats. For example, calcium hydroxide is written as Ca(OH)₂ — the OH group appears twice. Aluminum sulfate is Al₂(SO₄)₃ — the sulfate (SO₄) group appears three times. Our calculator supports nested brackets like Fe₄[Fe(CN)₆]₃ (Prussian blue). Simply type the formula as you would write it: Ca(OH)2, Al2(SO4)3, or Fe4[Fe(CN)6]3.

Use the middle dot symbol · (U+00B7) to separate the anhydrous compound from its water of crystallization. For example: CuSO₄·5H₂O (copper(II) sulfate pentahydrate) or Na₂CO₃·10H₂O (sodium carbonate decahydrate). You can also use a regular period . or bullet • as the separator. Click the · button next to the input field to easily insert the hydrate dot on mobile devices. The calculator automatically multiplies the water molecules by the hydrate coefficient and adds them to the total.

This calculator uses standard atomic weights based on IUPAC (International Union of Pure and Applied Chemistry) recommendations. Values are taken from the most recent IUPAC technical report, with atomic weights expressed to 3–4 decimal places for stable elements. For radioactive elements with no stable isotopes (such as Technetium, Promethium, and elements beyond Bismuth), the mass number of the most stable or longest-lived isotope is used. The atomic weights are regularly updated to reflect the latest scientific consensus.

Common reasons for unrecognized formulas include: (1) Element symbols must start with a capital letter — use Co for cobalt, not CO (which would be carbon + oxygen). (2) Check for balanced parentheses — every opening bracket must have a matching closing bracket. (3) Avoid leading numbers — the formula should not start with a coefficient (use H₂O, not 2H₂O). (4) Ensure you use standard element symbols — some older or non-standard symbols may not be recognized. (5) Remove any spaces within the formula. If you continue experiencing issues, try one of the example formulas to verify the calculator is working.

Molecular weight (or relative molecular mass) is a dimensionless quantity — the ratio of a molecule's mass to 1/12 of the mass of a carbon-12 atom. Molar mass is the mass of one mole of a substance, expressed in g/mol. Numerically, they are identical. For example, water has a molecular weight of 18.015 and a molar mass of 18.015 g/mol. In practice, the terms are often used interchangeably, and this calculator provides the molar mass in g/mol, which is the standard unit for laboratory and industrial calculations.

Yes! This calculator handles condensed organic formulas effectively. For example, CH₃COOH (acetic acid) is correctly parsed as C₂H₄O₂ (2 carbons, 4 hydrogens, 2 oxygens), yielding a molar mass of 60.052 g/mol. Similarly, C₂H₅OH (ethanol), CH₃CH₂OH, and other condensed formulas are parsed by summing all atom occurrences. The parser reads the formula character by character, accumulating element counts regardless of how the formula is notated — making it ideal for organic chemistry, biochemistry, and pharmaceutical calculations.

Mass percentages are calculated to high precision using the full atomic weight values stored in our database. Each element's contribution is computed as (atomic weight × number of atoms) / total molar mass × 100%. Results are displayed to 2 decimal places for percentages. The underlying calculations use double-precision floating-point arithmetic, ensuring accuracy suitable for academic research, quality control laboratories, and industrial applications. For the most demanding work, always verify against certified reference materials.