Mole Calculator

Master stoichiometry. Convert between Mass, Moles, and Particles instantly.

Calculation Data

g
g/mol

Example: H₂O = 18.015

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Enter values on the left to calculate the missing variable.

Understanding the Mole

The mole is the heart of stoichiometry. It provides a specific number (Avogadro's number) that lets us define "amounts" of atoms or molecules, allowing us to weigh out 12 grams of Carbon and know for a fact that we have exactly one mole of atoms.

Find Moles

n = m / M

Mass ÷ Molar Mass

Find Mass

m = n × M

Moles × Molar Mass

Find Particles

N = n × Nₐ

Moles × Avogadro

Avogadro's Constant

Why 6.022 × 10²³? This number was chosen so that the mass of one mole of a substance (in grams) is numerically equal to the average mass of one molecule (in daltons).

  • 1 atom of 12C weighs 12 daltons.
  • 1 mole of 12C weighs exactly 12 grams.

Practical Example

how many moles are in 50g of Water?

  1. Formula: H₂O
  2. Molar Mass: (2×1.01) + 16.00 = 18.02 g/mol
  3. Calculation: 50g / 18.02 g/mol
  4. Answer: 2.775 mol

Explore More Chemistry Tools

Molar Mass

Calculate molecular weight.

Stoichiometry

Mole ratios & reactions.

Percent Composition

Mass % of elements.

Frequently Asked Questions

What is a Mole in chemistry?

A mole is the SI unit for the amount of substance. One mole contains exactly 6.02214076 × 10²³ elementary entities (atoms, molecules, ions). This number is known as the Avogadro constant. Conceptually, it's just a count, similar to how a 'dozen' equals 12.

How do I convert Grams to Moles?

Use the formula: n = m / M. Divide the mass of your sample ($m$, in grams) by the substance's Molar Mass ($M$, in g/mol). For example, 18g of Water (M ≈ 18 g/mol) is exactly 1 mole.

How do I convert Moles to Atoms or Molecules?

Multiply the number of moles ($n$) by Avogadro's number ($N_A$): Number of Particles = n × 6.022 × 10²³. If you have 2 moles of Helium, you have roughly $1.2044 × 10^{24}$ helium atoms.

What is Molar Mass?

Molar mass is the mass of one mole of a substance, usually expressed in g/mol. It is numerically equivalent to the atomic (or molecular) mass found on the periodic table (in amu).

Why do chemists use the Mole?

Atoms are too tiny to count individually. The mole allows chemists to work with macroscopic amounts (grams) while still maintaining fixed ratios of atoms. It bridges the gap between the atomic world and the laboratory bench.

What is STP (Standard Temperature and Pressure)?

STP is defined as 0°C (273.15 K) and 1 atm pressure. At STP, one mole of any ideal gas occupies 22.4 liters. This allows for easy conversion between volume and moles for gases.

Can I use this calculator for ions?

Yes! The mole concept applies to any 'elementary entity'. You can have a mole of electrons, a mole of sodium ions (Na⁺), or a mole of photons. The math remains the exact same.

How do I find the molar mass of a compound?

Sum the atomic masses of all atoms in the formula. For CO₂: C (12.01) + 2 × O (16.00) = 44.01 g/mol.

What is the difference between Molality and Molarity?

Molarity (M) is moles per liter of solution (mol/L). Molality (m) is moles per kilogram of solvent (mol/kg). Molarity changes with temperature (volume expands), while Molality does not.

Is Avogadro's number exact?

Yes, as of the 2019 redefinition of SI base units, the Avogadro constant is fixed exactly at $6.02214076 \times 10^{23} mol^{-1}$.