Mol & Molar Mass
Calculator
Enter a chemical formula; instantly calculate molar mass, moles, particle count, STP gas volume and molarity.
Supported notation:H₂O · Ca(OH)₂ · K₄[Fe(CN)₆] · CuSO₄·5H₂O · Mg₃(Fe(CN)₆)₂ · Al₂(SO₄)₃·18H₂O
⚠ Capitalization matters: Co (Cobalt) ≠ CO (Carbon monoxide)
Guide to Moles and Molar Mass
The mole is the fundamental unit for amount of substance in chemistry. Converting between mass, moles, particle count and gas volume is central to exam-style chemistry.
Enter a chemical formula to find molar mass, convert mass ↔ mol ↔ particles, and work through molarity calculations step by step.
How to Calculate Moles
Enter the chemical formula
Type the formula using regular digits for subscripts (H2O, C6H12O6).
Read the molar mass
Ferrum parses the formula and computes molar mass (M, g/mol).
Choose mode and enter a value
Select Mass → Mol and enter mass in g, kg or mg.
Get the result: n = m ÷ M
Moles, particle count and STP gas volume are shown together.
Frequently Asked Questions
How do you calculate moles?
Moles equal mass (grams) divided by molar mass (g/mol): n = m / M. For example, 36 g of water: 36 ÷ 18.015 ≈ 2 mol.
How is molar mass calculated?
Molar mass is the sum of each element's standard atomic mass times its count in the formula. For Ca(OH)₂: 40.078 + 2×(15.999 + 1.008) = 74.093 g/mol.
What is Avogadro's number?
Avogadro's number (Nₐ = 6.022 × 10²³ mol⁻¹) is the number of particles in one mole. It links moles and particle count: N = n × Nₐ.
Why does capitalization matter in formulas?
"Co" is cobalt, while "CO" is carbon monoxide. Wrong capitalization gives completely different molar mass results.
How do you enter hydrate formulas?
Use a hydrate dot: CuSO₄·5H₂O or a decimal point: CuSO4.5H2O. The dot marks hydrate water, not a decimal; water molecules are counted separately.
How much volume does 1 mol of gas occupy at STP?
At STP (0°C, 1 atm), 1 mol of an ideal gas occupies 22.4 L.
Are molecular mass and molar mass the same?
Numerically yes, but units differ. Molecular mass is mass per molecule (u or Da). Molar mass is mass per mole (g/mol).
How is molarity (concentration) calculated?
Molarity is moles of solute per liter of solution: c = n / V (mol/L). Moles come from n = m / M. Example: 2 mol NaCl in 500 mL final volume → c = 2 / 0.5 = 4 mol/L (total solution volume, not water alone). This tool computes the others from mass, moles or molarity.
⚛️ Atom Simulations
Explore moles and atoms with visual simulations