# Molar Mass Calculator

URL: https://speedycalculator.com/calculators/chemistry/molar-mass/
Last updated: 2026-10-30

> Type any chemical formula – including brackets, hydrates and ions – to get its molar mass in g/mol together with a breakdown of every element: number of atoms, atomic mass, mass contribution and mass percent, plus a chart of the contributions.

## Inputs

- Chemical formula — Examples: H2O, Ca(OH)2, CuSO4·5H2O, [Cu(NH3)4]SO4, NH4+. Capital letters matter: Co is cobalt, CO is carbon monoxide.
- Amount to weigh out (optional) (mol, mmol, µmol, kmol)

## Results

- Molar mass
- Molar mass in kg/mol
- Formula (Hill notation)
- Atoms per formula unit
- Number of different elements
- Mass of the amount entered
- Element breakdown
- Mass contribution of each element

## Formula

```
M = Σ (nᵢ × Aᵢ) · nᵢ = number of atoms of element i in the formula · Aᵢ = standard atomic weight of element i (g/mol)
```

## Explanation

The molar mass of a substance is the mass of one mole of it – 6.022 × 10²³ formula units – expressed in grams per mole. Because the mole was defined so that one mole of carbon-12 weighs exactly 12 g, the molar mass of any compound in g/mol has the same number as the mass of one of its molecules in daltons. Water, H₂O, has a molar mass of 2 × 1.008 + 15.999 = 18.015 g/mol, so 18 g of water is one mole of water molecules.

To find a molar mass you multiply the atomic weight of each element by the number of times it appears in the formula and add everything up. Subscripts after a bracket multiply everything inside the bracket – Ca(OH)₂ contains two oxygen and two hydrogen atoms – and the water in a hydrate such as CuSO₄·5H₂O must be counted too.

This calculator reads the formula exactly as you would write it, uses IUPAC standard atomic weights and shows the full working as a table, so you can check each step or copy it into a lab report. Enter an amount in moles to also see how many grams you would need to weigh out.

### How to use the Molar Mass Calculator

- **Chemical formula** — Examples: H2O, Ca(OH)2, CuSO4·5H2O, [Cu(NH3)4]SO4, NH4+. Capital letters matter: Co is cobalt, CO is carbon monoxide.
- **Amount to weigh out (optional)**

Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.

### How it works

The formula is parsed into elements and atom counts (brackets and hydrate dots are multiplied out). Each count is multiplied by the standard atomic weight of the element, the products are summed to give the molar mass, and each product divided by the total gives the element's mass percent.

### Worked example

Glucose, C₆H₁₂O₆: carbon contributes 6 × 12.011 = 72.066 g/mol, hydrogen 12 × 1.008 = 12.096 g/mol and oxygen 6 × 15.999 = 95.994 g/mol. Adding them gives M = **180.156 g/mol**. Carbon makes up 72.066 ÷ 180.156 = 40.00% of the mass, hydrogen 6.71% and oxygen 53.28%. To prepare 0.5 mol you would weigh out 0.5 × 180.156 = 90.08 g.

### Molar masses of everyday substances

SubstanceFormulaMolar mass (g/mol)WaterH₂O18.015Carbon dioxideCO₂44.009Table saltNaCl58.44EthanolC₂H₅OH46.069Sulfuric acidH₂SO₄98.072Baking sodaNaHCO₃84.006GlucoseC₆H₁₂O₆180.156Copper(II) sulfate pentahydrateCuSO₄·5H₂O249.68

### Tips

- Type formulas with normal capitals and numbers, e.g. Ca(OH)2 or CuSO4·5H2O – brackets and hydrates work.
- Atomic masses are IUPAC standard atomic weights; radioactive elements use the mass number of their longest-lived isotope.
- Electronegativity values are on the Pauling scale.
- Everything is calculated in your browser.

### Common mistakes to avoid

- Writing CO (carbon monoxide) when you mean Co (cobalt) – capitals matter.
- Forgetting to multiply the bracket contents by the subscript after the bracket.
- Mixing up atomic number (protons) and mass number (protons + neutrons).

## Worked example

Inputs — Chemical formula: C6H12O6; Amount to weigh out (optional): 1 mol.

Results — **Molar mass = 180.156 g/mol**; Molar mass in kg/mol = 0.180156 kg/mol; Formula (Hill notation) = C₆H₁₂O₆; Atoms per formula unit = 24; Number of different elements = 3; Mass of the amount entered = 180.156.

## Key terms

- **Molar mass (M)**: Mass of one mole of a substance, in g/mol.
- **Standard atomic weight**: The average mass of an element's atoms in natural samples, relative to 1/12 of a carbon-12 atom (IUPAC).
- **Mole**: The SI unit of amount of substance: exactly 6.02214076 × 10²³ entities.
- **Formula unit**: The smallest repeating unit of an ionic compound, such as one NaCl.

## FAQ

**What is the molar mass of water?**
H₂O = 2 × 1.008 + 15.999 = 18.015 g/mol.

**What is the molar mass of glucose?**
C₆H₁₂O₆ = 6 × 12.011 + 12 × 1.008 + 6 × 15.999 = 180.156 g/mol.

**What is the molar mass of NaCl?**
22.990 + 35.45 = 58.44 g/mol.

**What is the molar mass of CO₂?**
12.011 + 2 × 15.999 = 44.009 g/mol.

**How do brackets work in a formula?**
The subscript after a bracket multiplies everything inside. Ca(OH)₂ has 1 Ca, 2 O and 2 H, giving 40.078 + 2 × 15.999 + 2 × 1.008 = 74.092 g/mol.

**How do I enter a hydrate?**
Use a dot, an asterisk or a full stop: CuSO4·5H2O, CuSO4*5H2O or CuSO4.5H2O. The water is included, giving 249.68 g/mol.

**Is molar mass the same as molecular weight?**
They have the same number but different units: molar mass is per mole (g/mol), molecular weight (molecular mass) is per molecule (u or Da).

**Why do some sources give slightly different values?**
Atomic weights vary a little in nature and tables round differently. This calculator uses the IUPAC conventional values, e.g. H = 1.008, C = 12.011, O = 15.999, Cl = 35.45.

**What formula does the Molar Mass Calculator use?**
M = Σ (nᵢ × Aᵢ) · nᵢ = number of atoms of element i in the formula · Aᵢ = standard atomic weight of element i (g/mol).


## Sources

- [IUPAC Commission on Isotopic Abundances and Atomic Weights – Standard atomic weights](https://www.ciaaw.org/atomic-weights.htm)
- [NIST – Periodic table of the elements](https://www.nist.gov/pml/periodic-table-elements)
- [OpenStax – Chemistry 2e](https://openstax.org/details/books/chemistry-2e)