Molar Mass Calculator
Sum atom counts multiplied by abridged standard atomic weights. Enter formulas such as H2O, Ca(OH)2, K4[Fe(CN)6], or CuSO4·5H2O.
Use element symbols, positive integer counts, () or [] groups, and · or . hydrate separators. Subscript digits are accepted. Only components after a hydrate separator may have a leading multiplier. No internal spaces, charges, isotopes, decimals, reaction equations, or mixture notation.
Limits: 256 characters, 4 nested groups, 8 hydrate components, 128 terms, each count/multiplier 1–1000, and 1,000,000 total atoms.
Approximate molar mass
| Element | Atom count | Atomic weight | Contribution (g/mol) | Mass percentage |
|---|
Uses the central values for the 84 elements with standard atomic weights in the CIAAW 2024 abridged table. Isotopic composition and source uncertainties are not propagated. Results display up to 6 significant digits, which does not imply measured accuracy. This is an educational estimate for ordinary material, not an isotope-specific or monoisotopic mass.
Atomic-weight source: CIAAW, Abridged Standard Atomic Weights 2024A QUICK WALKTHROUGH
How to use this tool
- Enter a case-sensitive chemical formula.
- Calculate the approximate molar mass.
- Review atom counts, atomic weights, mass contributions, and percentages.
Chemical formula
Use element symbols, positive integer counts, () or [] groups, and · or . hydrate separators. Subscript digits are accepted. Only components after a hydrate separator may have a leading multiplier. No internal spaces, charges, isotopes, decimals, reaction equations, or mixture notation. Limits: 256 characters, 4 nested groups, 8 hydrate components, 128 terms, each count/multiplier 1–1000, and 1,000,000 total atoms.
Atomic weights and precision
Uses the central values for the 84 elements with standard atomic weights in the CIAAW 2024 abridged table. Isotopic composition and source uncertainties are not propagated. Results display up to 6 significant digits, which does not imply measured accuracy. This is an educational estimate for ordinary material, not an isotope-specific or monoisotopic mass.
GOOD TO KNOW
Common questions
Can it interpret any chemical notation?
No. It counts atoms using the stated grammar; it does not validate chemical stability or bonding. The dot is always a hydrate separator, never a decimal point. All input stays in your browser.