Molar Mass Calculator

Enter a chemical formula (e.g., H2O, CuSO4.5H2O, Na2CO3)

Quick Answer – What is Molar Mass?

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in a chemical formula, where each element's atomic mass is taken from the periodic table. For example, the molar mass of water (H&sub2;O) is 18.015 g/mol.

Theory & Concept

The molar mass (M) of a compound is numerically equal to the sum of the relative atomic masses (Ar) of each element multiplied by its number of atoms in the molecular formula. The standard unit is g mol−1.

M = Σ (ni × Ar,i)

Where ni is the count of atoms of element i, and Ar,i is its standard atomic weight. For hydrated salts (e.g., CuSO4·5H2O), the mass of water molecules is added separately.

Atomic masses used in this calculator (IUPAC recommended, g/mol): H: 1.008, C: 12.011, N: 14.007, O: 15.999, Na: 22.990, Mg: 24.305, Al: 26.982, Si: 28.085, P: 30.974, S: 32.06, Cl: 35.45, K: 39.098, Ca: 40.078, Fe: 55.845, Cu: 63.546, Zn: 65.38, Br: 79.904, Ag: 107.87, I: 126.90, Ba: 137.33, plus more.

Solved Examples

Example 1: Glucose (C&sub6;H&sub1;&sub2;O&sub6;)

C: 6 × 12.011 = 72.066
H: 12 × 1.008 = 12.096
O: 6 × 15.999 = 95.994
Molar mass = 72.066 + 12.096 + 95.994 = 180.156 g/mol

Example 2: Copper(II) Sulfate Pentahydrate (CuSO&sub4;·5H&sub2;O)

Cu: 1 × 63.546 = 63.546
S: 1 × 32.06 = 32.06
O (from SO&sub4;): 4 × 15.999 = 63.996
5H&sub2;O: 5 × (2 × 1.008 + 15.999) = 5 × 18.015 = 90.075
Total = 63.546 + 32.06 + 63.996 + 90.075 = 249.677 g/mol

Example 3: Sodium Carbonate (Na&sub2;CO&sub3;)

Na: 2 × 22.990 = 45.98
C: 1 × 12.011 = 12.011
O: 3 × 15.999 = 47.997
Molar mass = 45.98 + 12.011 + 47.997 = 105.988 g/mol

Frequently Asked Questions

Q1. How do I enter a chemical formula correctly?
Use element symbols starting with an uppercase letter (e.g., H, Na, Cl) followed by optional lowercase letters. Subscripts are just numbers typed after the element (e.g., H2O). For hydrated salts, use a dot or asterisk: CuSO4.5H2O or CuSO4*5H2O. Parentheses are supported (e.g., Ca(NO3)2).
Q2. What atomic masses does the calculator use?
It uses standard IUPAC atomic weights (like those in NCERT and JEE data books). For example, carbon = 12.011, oxygen = 15.999, chlorine = 35.45. These are precise enough for all academic calculations. The complete list is embedded in the tool.
Q3. Can I calculate molar mass for a formula with parentheses?
Absolutely. Enter Ca(OH)2 or Al2(SO4)3. The calculator intelligently multiplies the group inside parentheses by the subscript that follows. Nested parentheses are not supported, but simple grouping works perfectly.
Q4. What if I make a typo in the formula?
If an element symbol isn't recognised (e.g., 'Xy'), the calculator will show an error and highlight the problematic token. It also catches unbalanced parentheses. Check spelling: all symbols are case‑sensitive (e.g., Co is cobalt, CO is carbon monoxide – but the formula must start with uppercase letters).
Q5. Why do some molar masses have decimals?
Because most elements in nature exist as a mixture of isotopes. The atomic mass is a weighted average of these isotopes, leading to non‑integer values like 35.45 for chlorine.