Molar Mass Calculator
Find the molar mass of any chemical formula, with a per-element breakdown of where the mass comes from.
What is Molar Mass?
Molar mass is the mass of one mole of a substance, in grams per mole. It is the number that takes you between the two things you can actually measure — a mass on a balance and a count of particles — so almost every chemistry calculation starts here. For a formula it is simply the sum of each element's atomic mass multiplied by how many atoms of it the formula contains.
How it works
The formula is parsed into element counts first: `Cu(NO3)2` becomes 1 copper, 2 nitrogens and 6 oxygens, and `CaSO4·2H2O` is handled as a hydrate whose second part is multiplied by two. Each count is then multiplied by the element's standard atomic weight and the results are summed. The breakdown table is that same sum, term by term, so the total can be checked rather than trusted.
- Enter what you know. Every field recalculates as you type — there is no submit button. Leave the quantity you want blank and the page solves for it.
- Read the answer and the working. The result appears above the fold; underneath it is the formula with your numbers substituted, so the arithmetic can be checked rather than trusted.
- Check the units and the size. Units are shown on every value and selectable per field, so a result in kJ, kPa or km/h is converted rather than assumed. Sanity-check the magnitude against a known landmark such as 1 g/cm³ for water.
Examples
A textbook problem with a known answer
Every tool here is checked against standard example problems — the molar mass of C6H12O6 is 180.16 g/mol, and free fall from 20 m takes about 2.02 s at g = 9.8 m/s².
A result you want to reason backwards from
Leave the quantity you already know blank instead: given the final answer, most tools recover the starting value — the mass needed for a target concentration, or the height a fall must have had.
Common mistakes
Forgetting that a formula is only as good as its subscripts
H2O and H2O2 are different compounds. The formula field shows its parse — element by element — so a mis-typed subscript is visible before it reaches the arithmetic.
Mixing units in the middle of a calculation
The most common source of a wrong answer is a value in grams next to a formula expecting kilograms, or Celsius next to a gas constant expecting kelvin. This category converts on the way in and labels what it used.
Frequently asked questions
What is the molar mass of glucose, C6H12O6?
180.16 g/mol — 6 × 12.011 (carbon) + 12 × 1.008 (hydrogen) + 6 × 15.999 (oxygen). Enter it above and the breakdown shows each term.
Do brackets and hydrates work?
Yes. Parentheses and square brackets are both supported and can nest, so Cu(NO3)2 and K4[Fe(CN)6] parse correctly. A hydrate written with a middle dot, such as CaSO4·2H2O, multiplies everything after the dot by the number in front of it.
How many decimal places should I use?
Molar masses here carry four decimal places, which is more than a typical textbook problem needs. Round the final answer to the number of significant figures the question gave you — the Significant Figures Calculator in Units & Numbers does that rounding for you.