Molecular Weight Calculator
Instantly compute the molar mass of any compound and see a detailed breakdown of its elemental mass percentages. Save time balancing your equations.
Last updated: March 3, 2026
(NH4)2SO4Typing Tips
Remember to use correct capitalization. Formulas are case-sensitive to differentiate elements. For instance, Co represents Cobalt, while CO means Carbon Monoxide.
18.015
Elemental Composition
| Element | Atoms | Mass (g) | Percent |
|---|---|---|---|
O | 1 | 15.999 | 88.81% |
H | 2 | 2.016 | 11.19% |
Understanding Molar Mass
Chemical compounds are combinations of different elements. A molecular weight calculation simply counts the combined weight of every atom in the molecule.
What Does g/mol Mean?
Grams per mole (g/mol) provides a bridge between two worlds: the microscopic world of atoms and the macroscopic world of laboratory scales. Because a single atom weighs practically nothing, chemists measure them in "moles" (groups of ~6.022 × 10²³ atoms).
Looking at the periodic table, Carbon has an atomic mass of ~12. That means one mole of Carbon weighs exactly 12 grams.
Formula Expansion
Whenever you see parenthesis in a chemical formula followed by a number, that number is a multiplier for everything inside.
Number of Al atoms = 2
Number of S atoms = 1 × 3 = 3
Number of O atoms = 4 × 3 = 12
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