Calculate relative molecular or formula mass
The molecular weight calculator expands a chemical formula and adds the relative atomic-mass contribution of every element. Enter a molecule such as H2O or C6H12O6, or a formula unit such as NaCl when the substance is not made of discrete molecules. The result is dimensionless relative molecular mass for a molecule or relative formula mass for an ionic or network substance. Every element count and subtotal remains visible for checking.
Add atomic-weight contributions
For each element, multiply its formula count by its relative atomic mass and add the products. Glucose therefore contains six carbon, twelve hydrogen, and six oxygen contributions. Parentheses, square brackets, and hydrate dots are expanded before the sum. Element symbols are case-sensitive, and a leading reaction coefficient is rejected because it describes several formula units rather than changing the relative mass of one unit.
Distinguish molecular weight from molar mass
Relative molecular mass has no unit because it compares one molecule with the atomic-mass scale. Molar mass describes the mass of one mole and is expressed in g/mol. Their numerical values often match when the same conventional atomic weights and chemical formula are used, which is why the terms are sometimes mixed in informal writing. A correct answer should still name the requested quantity and attach g/mol only when the problem asks for molar mass.
Check formula syntax and the total
Confirm the expanded atom counts before trusting the sum. Co means cobalt, while CO means carbon and oxygen; a missing capital letter changes the substance. Hydrate water and grouped ions must retain their multipliers. Recalculate one element subtotal and verify that all displayed contributions add to the reported relative mass. A specified isotope or enriched material can require isotope-specific masses instead of the conventional atomic weights used here.
Interpretation limits and private use
The result does not determine chemical name, structure, purity, isotope distribution, concentration, physical state, or whether the formula represents a stable substance. For ionic solids, “relative formula mass” is usually the clearer term because there may be no individual molecule. Use evaluated isotope data when exact isotope mass matters and retain the formula with any copied value. This page is an educational calculation rather than analytical identification.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.