Molar Mass Calculator
Type a formula. Brackets, square brackets and hydrates all work, and you get the breakdown by element.
Examples:
Grams and moles
g
mol
About this tool
This molar mass calculator reads a chemical formula and adds up the atomic masses for you. It handles brackets, square brackets and hydrates, so H2SO4, Ca(OH)2, K4[Fe(CN)6] and CuSO4·5H2O all work. You get the molar mass in g/mol, a table showing each element's share, and the working, plus a converter between grams and moles for mole calculations.
Tips
- A number after a bracket multiplies everything inside it. Ca(OH)2 contains 1 calcium, 2 oxygen and 2 hydrogen atoms, and Mg3(PO4)2 contains 2 phosphorus and 8 oxygen atoms.
- To find moles from a mass, divide by the molar mass: 36.04 g of water (H2O, 18.02 g/mol) is 2 mol.
- Percentage by mass is the element's subtotal divided by the molar mass, times 100. It is the number you need for percentage composition questions.
FAQ
- Which atomic masses does it use?
- Standard atomic weights from IUPAC, rounded. Your textbook or data sheet may round some values differently (for example Cl as 35.5), so the last decimal place can differ.
- How do hydrates work?
- The part after the dot is added on, multiplied by its number. CuSO4·5H2O is CuSO4 (159.61 g/mol) plus 5 H2O (90.08 g/mol), which gives 249.69 g/mol.
- Why do I get an error?
- Usually a symbol in the wrong case or an unmatched bracket. The error appears under the box and names the problem, for example an unknown symbol such as Xy or a ( without its ).