Moles & Molar Mass Calculator
Calculate moles, mass, or molar mass using the relationship between the amount of substance, mass, and molar mass. Choose the calculation mode and enter the known values.
Calculate Moles, Mass & Molar Mass
Select what you want to calculate, enter the two known quantities, and get the result with a step-by-step calculation.
Calculation Result
Step-by-Step Calculation
What Is a Mole in Chemistry?
A mole is the SI unit used to measure the amount of a substance. It provides a convenient way to describe very large numbers of atoms, molecules, ions, or other particles.
One mole contains exactly 6.02214076 × 1023 specified elementary entities. This number is known as the Avogadro constant.
Because individual atoms and molecules are extremely small, chemists use moles to work with measurable quantities of substances in laboratory and industrial calculations.
What Is Molar Mass?
Molar mass is the mass of one mole of a substance. It is commonly expressed in grams per mole (g/mol).
The molar mass of a compound can be determined from the atomic masses of the elements in its chemical formula. For example, water, H2O, has a molar mass of approximately 18.015 g/mol.
Molar mass connects microscopic chemical quantities with measurable mass and is widely used in stoichiometry, laboratory preparation, and chemical analysis.
How to Use the Moles & Molar Mass Calculator
- Select what you want to calculate.
- Enter the known mass, amount of substance, or molar mass required by the selected mode.
- Select the appropriate mass unit when entering mass.
- Enter molar mass in grams per mole when required.
- Click Calculate.
- Review the result and step-by-step calculation.
Moles and Molar Mass Formulas
The relationship between mass, moles, and molar mass can be rearranged depending on which quantity is unknown.
n = m ÷ M
Calculate Mass
m = n × M
Calculate Molar Mass
M = m ÷ n
In these formulas, n represents the amount of substance in moles, m represents mass in grams, and M represents molar mass in grams per mole.
Understanding the Variables
n — Amount of Substance
The symbol n represents the amount of substance and is measured in moles (mol).
m — Mass
The symbol m represents the mass of the sample. The standard calculation uses grams (g).
M — Molar Mass
The symbol M represents molar mass and is measured in grams per mole (g/mol).
Moles Calculation Example
Example: Suppose you have 18 g of water and the molar mass of water is approximately 18.015 g/mol.
Step 1: Mass = 18 g and molar mass = 18.015 g/mol.
Step 2: Use the formula: n = m ÷ M.
Step 3: n = 18 ÷ 18.015 ≈ 0.999 mol.
Therefore, 18 g of water corresponds to approximately 0.999 mol of water.
Mass Units and Unit Conversion
Molar mass is normally expressed in grams per mole, so mass must be converted to grams before applying the formula.
1 kg = 1,000 g
1 g = 1,000 mg
1 mg = 1,000 µg
The calculator performs these mass conversions automatically when kilograms, milligrams, or micrograms are selected.
How to Find the Molar Mass of a Compound
To determine the molar mass of a compound, add the atomic masses of all atoms represented in its chemical formula. Each element’s atomic mass is multiplied by the number of atoms of that element in the formula.
Example: Water
Water has the formula H2O. Its molar mass is approximately calculated as:
2 × 1.008 + 15.999
≈ 18.015 g/mol
The exact value used can vary slightly depending on the atomic-weight values and conventions used in a particular reference.
Common Uses of Moles and Molar Mass
- Stoichiometric calculations
- Laboratory solution preparation
- Chemical reaction calculations
- Determining the amount of a substance from its mass
- Converting between mass and amount of substance
- Chemistry education and laboratory exercises
Frequently Asked Questions
What is the formula for calculating moles?
The basic formula is n = m ÷ M, where n is the amount of substance in moles, m is mass in grams, and M is molar mass in grams per mole.
What is the formula for calculating mass?
Mass can be calculated using m = n × M, where n is the amount of substance in moles and M is molar mass in g/mol.
What is the formula for calculating molar mass?
Molar mass can be calculated using M = m ÷ n when the mass and amount of substance are known.
What unit is used for molar mass?
Molar mass is commonly expressed in grams per mole (g/mol).
Does the calculator convert kilograms and milligrams?
Yes. You can enter mass in grams, kilograms, milligrams, or micrograms. The calculator converts the selected mass to grams before performing the calculation.
Can this calculator calculate the molar mass of a chemical formula?
No. This calculator requires the molar mass to be entered when calculating moles or mass. It does not automatically parse chemical formulas or look up atomic masses.
Moles & Molar Mass Calculator Disclaimer
This calculator is provided for general educational and informational purposes only. Results depend on the values entered by the user, including mass and molar mass. Chemical calculations should be checked against appropriate scientific references, laboratory procedures, course materials, or qualified professionals when accuracy is important. This tool does not replace laboratory procedures, professional scientific judgment, or authoritative chemical data.