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. For example, water (H₂O) has a molar mass of approximately 18.015 g/mol — the sum of two hydrogen atoms (2 × 1.008) and one oxygen atom (15.999).
Why Molar Mass Matters
Stoichiometry
Solution Preparation
Yield Calculations
Analytical Chemistry
How to Use
Enter Chemical Formula
Type any chemical formula in the input field (e.g., H2O, NaCl, C6H12O6)
View Results Instantly
The molar mass, elemental breakdown table, and composition bar update in real time as you type
Use Quick Presets
Click any of the 12 common formula chips for instant calculation
Review History
Previously calculated formulas are saved and can be clicked to recalculate
Supported Formula Notation
| Notation | Example | Description |
|---|---|---|
| Simple formula | H2O, NaCl, CO2 |
Standard chemical formulas |
| Parentheses | Ca(OH)2, Mg3(PO4)2 |
Polyatomic groups with multiplier |
| Hydrates | CuSO4·5H2O |
Use · or . as separator |
| Brackets | [Fe(CN)6]4- |
Complex ions (charge ignored) |
Features
Real-Time Calculation
Results update instantly as you type. No need to press a button — the molar mass, breakdown table, and composition chart all refresh with every keystroke.
- Instant feedback
- No button clicks required
- Live data updates
Elemental Breakdown Table
A detailed table shows each element in the formula with comprehensive data:
- Element symbol and name (e.g., O — Oxygen)
- Atom count — how many atoms of this element
- Atomic mass — standard atomic weight in g/mol
- Total mass — count × atomic mass
- Percentage — mass contribution as % of total
Composition Bar
A color-coded horizontal bar visually represents the mass percentage of each element, making it easy to see which elements dominate the compound.
- Visual representation
- Color-coded elements
- Instant composition insight
Quick Presets
Twelve common chemical formulas are available as clickable chips:
- H₂O, NaCl, CO₂, H₂SO₄
- NaOH, C₆H₁₂O₆, CaCO₃
- C₂H₅OH, Ca(OH)₂, NH₃, HCl, Fe₂O₃
Calculation History
Every formula you calculate is automatically saved to your browser's local storage.
- Click any history item to recalculate
- Clear entire history with one click
- Up to 20 recent formulas stored
Frequently Asked Questions
What is the difference between molar mass and molecular weight?
They are often used interchangeably. Molar mass is the mass of one mole of a substance in grams per mole (g/mol), while molecular weight is technically a dimensionless ratio. In practice, both give the same numerical value for molecular compounds.
How accurate are the atomic masses?
This calculator uses standard atomic weights as recommended by IUPAC, covering all 118 elements. Values are rounded to 3-4 significant figures, which is sufficient for most chemistry calculations.
Can I enter hydrated compounds?
Yes. Use the middle dot (·) or a period (.) to separate the main compound from the water of crystallization.
Examples:
CuSO4·5H2O— copper(II) sulfate pentahydrateCuSO4.5H2O— alternative notation (also works)
Both formats calculate correctly.
What happens with charge notation?
Charge notation like 4- or 2+ at the end of a formula is automatically ignored. The calculator focuses on the elemental composition regardless of ionic charge.
Is my data stored anywhere?
Calculation history is stored only in your browser's local storage. No data is sent to any server — all calculations happen entirely in your browser.
- 100% client-side processing
- No server communication
- Complete privacy
- Data stays on your device
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