Molar Mass Calculator Formula
Understand the math behind the molar mass calculator. Each variable explained with a worked example.
Formulas Used
Molar Mass
molar_mass = mass_elem_a * count_a + mass_elem_b * count_b + mass_elem_c * count_cVariables
| Variable | Description | Default |
|---|---|---|
mass_elem_a | Atomic Mass of Element A(g/mol) | 12.011 |
count_a | Number of A Atoms | 6 |
mass_elem_b | Atomic Mass of Element B(g/mol) | 1.008 |
count_b | Number of B Atoms | 12 |
mass_elem_c | Atomic Mass of Element C(g/mol) | 15.999 |
count_c | Number of C Atoms | 6 |
How It Works
How to Calculate Molar Mass
Formula
Mw = sum of (atomic mass × count) for each element
Look up atomic masses on the periodic table and multiply by the subscript in the formula.
Worked Example
Glucose C6H12O6: C=12.011, H=1.008, O=15.999.
- 01C: 12.011 × 6 = 72.066
- 02H: 1.008 × 12 = 12.096
- 03O: 15.999 × 6 = 95.994
- 04Mw = 72.066 + 12.096 + 95.994 = 180.156 g/mol
Frequently Asked Questions
What is molar mass?
The mass of one mole of a substance in grams, numerically equal to the molecular weight in atomic mass units.
Where do I find atomic masses?
On the periodic table. Common ones: H=1.008, C=12.011, N=14.007, O=15.999, Na=22.990, Cl=35.453.
What if my compound has more than 3 elements?
Set unused element counts to zero and calculate remaining elements separately, then add.
Learn More
Guide
How to Balance Chemical Equations
Step-by-step guide to balancing chemical equations. Learn the law of conservation of mass, inspection method, tips for complex equations, and common mistakes.
Ready to run the numbers?
Open Molar Mass Calculator