Molar Mass Calculator
Enter a chemical formula to get its molar mass and convert between moles and grams.
This free molar mass calculator parses any chemical formula — including groups in parentheses like Ca(OH)2 or Al2(SO4)3 — and adds up the standard atomic weights of every atom to give you the molar mass in grams per mole (g/mol). It also includes a built-in mole-to-gram converter, so once you know the molar mass you can immediately find how many grams a given number of moles weighs, or vice versa.
Molar mass is one of the most frequently used values in chemistry, from balancing equations and preparing solutions of a specific molarity to calculating reaction yields. This tool uses the standard atomic weights published for each element, so results match the values found in standard periodic tables.
Frequently Asked Questions
What is molar mass?
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, expressed in grams per mole (g/mol). It is numerically equal to the sum of the standard atomic weights of all atoms in the formula.
How do I write a formula for this calculator?
Use standard chemical notation: element symbols with a capital first letter (Na, Cl, Ca), followed by an optional number for the count of atoms, and parentheses for repeated groups, e.g. H2SO4, C6H12O6, Ca(OH)2, Al2(SO4)3.
How is molar mass calculated?
Multiply the atomic weight of each element by the number of times it appears in the formula, then add all the results together. For example, H2O = (2 × 1.008) + 15.999 = 18.015 g/mol.
Can I use nested parentheses like Ca(OH)2?
Yes. The calculator correctly multiplies every atom inside the parentheses by the subscript that follows the closing bracket, so Ca(OH)2 counts 1 Ca, 2 O and 2 H.
Does this calculator support hydrates like CuSO4·5H2O?
Not directly with the dot notation. To calculate a hydrate, compute the molar mass of the anhydrous compound and the water separately, then add (molar mass of water × number of water molecules) to the anhydrous molar mass.
How accurate are the atomic weights used?
The calculator uses standard atomic weights (conventional values) for all 118 elements as published by international chemistry authorities, matching the values on a typical periodic table.
How do I convert grams to moles?
Divide the mass in grams by the molar mass in g/mol. This calculator does that automatically once you enter a formula — just type a gram amount and it shows the equivalent moles, or the reverse.
What is the molar mass of water?
Water (H2O) has a molar mass of approximately 18.015 g/mol: two hydrogen atoms (1.008 each) plus one oxygen atom (15.999).
Why does my formula show an error?
Check that every element symbol starts with a capital letter and matches a real element (for example "Co" is cobalt, but "CO" is read as one carbon and one oxygen atom). Also make sure parentheses are balanced.
Can I calculate molar mass for organic molecules?
Yes, as long as you write the full molecular formula. For example, glucose is C6H12O6 and gives a molar mass of about 180.16 g/mol.