Molar Mass Calculator

You type a chemical formula, and it reads each element, multiplies its atomic mass by how many atoms are present, and adds it all up. It handles parentheses and subscripts, so it understands something like Ca(OH)2 the way you'd write it. It then shows the total along with a breakdown of every element's share. Everything runs in your browser, so you'll see the mass the moment you finish typing, and nothing you enter leaves your device.

You add up the atomic mass of every atom in the formula. Look up each element on the periodic table, multiply its atomic mass by the number of those atoms, then total the parts. Water, H2O, has two hydrogens at about 1.008 and one oxygen at 16.00, so 2 times 1.008 plus 16.00 is 18.02 grams per mole. The calculator does that lookup and arithmetic for you, even with brackets, so you don't have to chase atomic masses one by one.

For everyday purposes, yes, the numbers match, though they mean slightly different things. Molar mass is the mass of one mole of a substance in grams per mole, while molecular weight is the mass of one molecule relative to atomic mass units. They come out to the same figure for a given formula, so a molar mass of 18.02 grams per mole and a molecular weight of 18.02 describe water equally well. This tool reports the value you'd use for either.

Use standard notation: capital first letter for each element, lowercase second letter if it has one, and a number after for the count. So sodium chloride is NaCl and glucose is C6H12O6. Use round brackets for repeated groups, like Ca(OH)2 for calcium hydroxide, and the number after the bracket multiplies everything inside. The tool is case-sensitive, since Co is cobalt while CO is carbon monoxide, so type elements exactly as they appear on the table.

Because element symbols are case-sensitive, and a slip changes the meaning. The first letter is always uppercase and any second letter is lowercase, so Mg is magnesium but mg is not an element at all. The classic trap is CO versus Co: carbon monoxide is one carbon and one oxygen, while Co is the single element cobalt. If the calculator flags an element it doesn't recognize, check that you've capitalized it the way the periodic table does.

Yes, it's completely free, with no sign-up, and it runs right in your browser, so nothing you enter leaves your device. Type a formula, tap an example to try one, and read the molar mass with its element breakdown in a tap. Bookmark it for chemistry homework, stoichiometry, or making up solutions, and pair it with the molarity tool, which needs exactly this number to turn grams into a concentration.