Science
Molarity
Calculate solution molarity from amount of substance and solution volume.
Calculators / Science / Molecular weight from composition
Molecular weight from composition calculator
Calculate molar mass from counts of two elements and their atomic masses.
On this page
Molar mass18.02G/mol
Calculator controls
How to calculate
Calculate molar mass from counts of two elements and their atomic masses.
Molar mass = count1*mass1+count2*mass2
Worked example
Element 1 atom count: 2; Element 1 atomic mass: 1.008; Element 2 atom count: 1; Element 2 atomic mass: 15.999.
Molar mass: 18.02 g/mol.
Assumptions and limits
Enter atomic masses from a current reference and extend the calculation manually for compounds with more than two element types.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Calculate molar mass from counts of two elements and their atomic masses. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the molecular weight from composition to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Element 1 atom count | Enter a number of at least 0 and no more than 1000. |
| Element 1 atomic mass | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Element 2 atom count | Enter a number of at least 0 and no more than 1000. |
| Element 2 atomic mass | Enter a number of at least 0.000001 and no more than 1000000000000. |
Frequently asked questions
What should I check before using the molecular weight from composition result?
Enter atomic masses from a current reference and extend the calculation manually for compounds with more than two element types.
Is this molecular weight from composition result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.