Molecular Weight Calculator - Calculate Molar Mass Easily

Calculate molecular weight instantly from any chemical formula.

Enter Chemical Formula (e.g., H2O) or Select from List:

Creator

Mounir Roukky

Page Contents

Our Molecular Weight Calculator is a handy tool that helps you find the weight of a molecule, known as its molecular weight or molar mass, by entering its chemical formula (like H₂O or CO₂).

This weight is measured in grams per mole (g/mol) and tells you how heavy one mole of that substance is. It’s super useful in chemistry for understanding how much of a substance you’re working with, especially when mixing chemicals or studying their properties. Learn more about molar mass basics to deepen your understanding.

How to Use Molecular Weight Calculator

Scroll up to the calculator’s section or click here: https://molaritycalc.com/molecular-weight-calculator/
Enter the chemical formula of the substance (e.g., H2O for water) in the field.
Click the ‘Calculate’ button to get the molecular weight.
The result will display in grams per mole (g/mol) with three decimal places.
Use standard element symbols (e.g., C for carbon, O for oxygen) and numbers for atoms (e.g., H2O for two hydrogens).

Tips for Using the Calculator:

Use uppercase letters for element symbols (e.g., H2O, not h2o).
Check the periodic table for atomic weights if unsure.
Start with simple formulas like H2O to get the hang of it.

Who Can Use the Calculator?

This molecular weight calculator is ideal for chemistry students tackling homework, professional chemists in labs, and teachers explaining molecular concepts. It’s perfect for anyone needing fast, accurate calculations for experiments or education, especially when paired with resources like what is a mole in chemistry.

Formula and Examples

To figure out the molecular weight, you add up the weights of all the atoms in a molecule. Each element has a weight (called atomic weight) based on its protons and neutrons, listed on the periodic table.

For example, water (H₂O) has two hydrogen atoms (each about 1.008) and one oxygen (about 15.999), so you add them up to get the total weight per mole.

This helps you know how much of a substance you have when you weigh it, like counting how many mole-sized piles you can make!

Examples:
Let’s try some examples together to see how it works. You can test these in the calculator.
1. Water (H₂O):
  - Formula: H2O
  - Calculation: 2 × 1.008 (H) + 15.999 (O) = 18.015 g/mol
  - Explanation: Two hydrogens and one oxygen make 18.015 grams per mole. Enter H2O, and you’ll see 18.015 g/mol!
2. Carbon Dioxide (CO₂):
  - Formula: CO2
  - Calculation: 12.011 (C) + 2 × 15.999 (O) = 44.009 g/mol
  - Explanation: One carbon and two oxygens give 44.009 grams per mole. Try CO2 in the calculator!
3. Methane (CH₄):
  - Formula: CH4
  - Calculation: 12.011 (C) + 4 × 1.008 (H) = 16.043 g/mol
  - Explanation: One carbon and four hydrogens make 16.043 grams per mole. Test CH4 to confirm!
4. Aluminum Sulfate (Al₂(SO₄)₃):
  - Formula: Al2(SO4)3
  - Calculation: 2 × 26.982 (Al) + 3 × 32.06 (S) + 12 × 15.999 (O) = 342.132 g/mol
  - Explanation: Two aluminums, three sulfurs, and twelve oxygens total 342.132 grams per mole. Enter Al2(SO4)3!
5. Glucose (C₆H₁₂O₆):
  - Formula: C6H12O6
  - Calculation: 6 × 12.011 (C) + 12 × 1.008 (H) + 6 × 15.999 (O) = 180.156 g/mol
  - Explanation: Six carbons, twelve hydrogens, and six oxygens make 180.156 grams per mole. Try C6H12O6!

Frequently Asked Questions (FAQ)

What is molecular weight?

Molecular weight is the total weight of a molecule, found by adding the weights of all its atoms. It’s usually the same as molar mass in everyday use.

How do I find the molar mass of a compound?

To find the molar mass, add up the atomic masses of all the atoms in the compound. You can find the atomic mass of each element on the periodic table. Multiply each atomic mass by how many atoms of that element are in the molecule, then add them all together. The answer is in grams per mole (g/mol).

Can I use this for complex formulas?

Yes, it supports basic formulas (e.g., Al₂(SO₄)₃) with up to two bracket levels, but ensure correct syntax.

How is molecular weight different from molar mass?

Molecular weight is the mass of one molecule in atomic units, while molar mass is the mass of one mole of molecules in grams per mole. For most purposes, they have the same numerical value.

Why is molecular weight important?

Molecular weight is important because it helps scientists figure out how much of a substance to use in reactions, make solutions, or convert between grams and moles.

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