Molecular Weight Calculator
Chemical formula → molar mass (g/mol)
Molecular weight
194.194g/mol
| Element | Atoms | At. wt | Mass | % |
|---|---|---|---|---|
| C | 8 | 12.011 | 96.088 | 49.48% |
| N | 4 | 14.007 | 56.028 | 28.85% |
| O | 2 | 15.999 | 31.998 | 16.48% |
| H | 10 | 1.008 | 10.08 | 5.19% |
ƒ MW = Σ (atomic weight × number of atoms)
The molecular weight (molar mass) of a compound is the sum of the standard atomic weights of every atom in its chemical formula, in grams per mole (g/mol). For example, caffeine (C₈H₁₀N₄O₂) is 194.19 g/mol. Enter any formula above — including hydrates such as CuSO₄·5H₂O and bracketed groups such as Ca(OH)₂ — to get the molar mass plus a per-element mass and percentage breakdown.
How to calculate molecular weight
Multiply the atomic weight of each element by the number of atoms of that element in the formula, then add the contributions together. For water (H₂O): (2 × 1.008) + (1 × 15.999) = 18.015 g/mol.
This calculator parses the formula for you, including subscripts, parentheses, square brackets and hydrate dots, and shows exactly how each element contributes to the total mass.
What you use molecular weight for
Molar mass is the bridge between grams and moles. You need it to prepare solutions of a known molarity, to convert a mass into an amount of substance, to calculate yields, and to read or compare a Certificate of Analysis.
Once you have the molecular weight, the Molarity and Solution Preparation calculators turn it into a concrete weighing for the bench.
Supported formula formats
Element symbols are case-sensitive (Co = cobalt, CO = carbon monoxide). Counts follow the element or a bracketed group, e.g. C8H10N4O2, Ca(OH)2, K4[Fe(CN)6]. For hydrates use a dot: MgSO4·7H2O. Unicode subscripts (C₈H₁₀) are accepted too.
Frequently asked questions
What is the difference between molecular weight and molar mass?
In everyday practice they are used interchangeably. Molecular weight (or molecular mass) is a dimensionless ratio relative to ¹²C, while molar mass is the same number expressed in grams per mole (g/mol). This calculator reports the molar mass in g/mol.
How do I enter a hydrate like copper sulfate pentahydrate?
Use a dot for the water of crystallisation: CuSO4·5H2O or CuSO4.5H2O both work. The calculator adds five water molecules (90.08 g/mol) to the anhydrous salt for a total of 249.68 g/mol.
Can it handle brackets and complex ions?
Yes. Parentheses and square brackets with multipliers are supported, e.g. Ca(OH)2 or K4[Fe(CN)6]. Nested groups are summed correctly.
Which atomic weights are used?
Standard atomic weights (IUPAC conventional values, g/mol) for all 118 elements. Results are typically accurate to within 0.01–0.1 g/mol of published values.
Is the molecular weight calculator free?
Yes — it runs entirely in your browser, with no sign-up. Tech Serve Solutions provides it as a free reference for chemists and procurement teams.
Need the actual compound — not just the maths?
Tech Serve Solutions supplies laboratory reagents, fine chemicals and pharmaceutical intermediates to USP, BP and EP grade, with a Certificate of Analysis and worldwide despatch.