g to mol Converter
To convert g to mol, divide the value in grams by the molecular weight (g/mol).
How to Convert g to mol
This g to mol converter tells you how many moles are in a given mass. Enter the mass in grams and the molecular weight of the substance.
To convert grams to moles, divide the mass by the molecular weight: moles = grams ÷ molecular weight (g/mol).
For example, water (H₂O) has a molecular weight of about 18.015 g/mol. So 36 g of water is 36 ÷ 18.015 ≈ 1.998 mol.
mol = g ÷ MWDivide the mass in grams by the molecular weight (g/mol) to get moles.Conversion Formula
The formula to convert g to mol is:
Where:
- g = mass in grams
- mol = amount in moles
- MW = molecular weight (molar mass) in g/mol
Conversion Table
Common g to mol conversions are shown below. The last column uses water (MW 18.015 g/mol) as an example.
| g | mol (formula) | mol for water |
|---|---|---|
| 0.01 | 0.01 ÷ MW | 0.0005550929781 |
| 0.1 | 0.1 ÷ MW | 0.005550929781 |
| 0.33 | 0.33 ÷ MW | 0.01831806828 |
| 0.5 | 0.5 ÷ MW | 0.0277546489 |
| 1 | 1 ÷ MW | 0.05550929781 |
| 2.5 | 2.5 ÷ MW | 0.1387732445 |
| 5 | 5 ÷ MW | 0.277546489 |
| 10 | 10 ÷ MW | 0.5550929781 |
| 33 | 33 ÷ MW | 1.831806828 |
| 50 | 50 ÷ MW | 2.77546489 |
| 100 | 100 ÷ MW | 5.550929781 |
| 250 | 250 ÷ MW | 13.87732445 |
| 500 | 500 ÷ MW | 27.7546489 |
| 1,000 | 1,000 ÷ MW | 55.50929781 |
Worked Examples
Here are some common examples of g to mol conversion, using water (MW 18.015 g/mol):
- 0.05550929781 mol = 1 g
- 0.277546489 mol = 5 g
- 1.831806828 mol = 33 g
- 5.550929781 mol = 100 g
Unit Definitions
What is a gram (g)?
The gram (g) is a unit of mass. It is one thousandth of a kilogram, the SI base unit of mass.
In the lab, grams are used to weigh out chemicals and to state molar mass in g/mol.
What is a mole (mol)?
The mole (mol) is the SI base unit for amount of substance. It counts particles, such as atoms, molecules or ions.
Since 2019, one mole contains exactly 6.02214076 × 1023 particles. This number is the Avogadro constant.
Why Is Molecular Weight Needed?
Moles count particles. Grams measure mass. One particle of each substance has its own mass, so the link between them is the molecular weight (MW), also called molar mass.
MW tells you how many grams one mole of a substance weighs. For example, one mole of water weighs about 18.015 g, while one mole of glucose weighs about 180.16 g.
Therefore, to convert g to mol, you divide by MW. Both units use the same prefix size, so no extra step is needed.
Uses and Importance of g and mol
Balances measure mass, but chemistry works in moles. Converting grams to moles lets you use a weighed amount in a chemical equation.
Stoichiometry
To find how much product a reaction can make, first convert each reactant mass into moles.
Checking concentrations
If you dissolved a known mass in a known volume, converting to moles lets you work out the concentration in mol/L.
Counting particles
Once you have moles, multiply by the Avogadro constant (6.02214076 × 1023 per mole) to get the number of molecules.
Frequently Asked Questions (FAQ)
What is the formula for g to mol?
moles (mol) = mass (g) ÷ molecular weight (g/mol).
How many moles are in 1 g of water?
1 ÷ 18.015 ≈ 0.05551 mol.
How many molecules are in 18 g of water?
18 g of water is almost exactly 1 mol, so it holds about 6.0 × 1023 molecules.
Can I convert grams to moles without the molecular weight?
No. Different substances have different masses per mole, so the molecular weight is always needed.
Does it matter if my sample is not pure?
Yes. The calculation assumes 100% pure substance. For an impure sample, first multiply the mass by the purity fraction.
Other Related Tools
Accuracy and Scope
The answer depends on the molecular weight you enter. Check whether your product is a salt, hydrate or free form, as each has a different molecular weight.
Example values use standard atomic weights and are rounded.
Sources