Molecular Weight Calculator

Calculate molecular weight (molar mass) from chemical formulas

Your Input

Examples: H2O, CO2, NaCl, Ca(OH)2, Al2(SO4)3, CuSO4·5H2O

Enter a chemical formula (e.g., H2O, C6H12O6, Ca(OH)2), then click Calculate to see molecular weight, element breakdown, and step-by-step solution.

Complete User Guide

What is Molecular Weight?

Molecular weight (also called molar mass) is the sum of the atomic weights of all atoms in a molecule. It is expressed in grams per mole (g/mol) and is used to convert between mass and moles in chemical calculations.

How to Use

  1. Enter the chemical formula in the input field
  2. Use proper capitalization (e.g., H2O, not h2o)
  3. Click Calculate to see molecular weight, breakdown, and step-by-step solution
  4. Use Reset to clear and hide results

Formula Format

  • Simple formulas: H2O, CO2, NaCl
  • With parentheses: Ca(OH)2, Al2(SO4)3
  • With hydrates: CuSO4·5H2O
  • Complex formulas: C6H12O6, C8H10N4O2

Formula Rules

  • Element symbols start with uppercase letter
  • Subscripts indicate number of atoms
  • Parentheses group atoms with multipliers
  • Use · or * for hydrate notation
  • No spaces in formulas

Calculation

Molecular Weight:

MW = Σ(Atomic Weight × Count)

For each element in the formula

Common Examples

H2O: Water (18.015 g/mol)

CO2: Carbon dioxide (44.009 g/mol)

NaCl: Sodium chloride (58.443 g/mol)

C6H12O6: Glucose (180.156 g/mol)

Ca(OH)2: Calcium hydroxide (74.093 g/mol)

Important Notes

  • Element symbols are case-sensitive
  • All elements must be valid chemical symbols
  • Parentheses must be properly balanced
  • Results are rounded to 4 decimal places
  • Mass percentages sum to 100%

Common Applications

  • Converting between mass and moles
  • Preparing solutions of known concentration
  • Stoichiometry calculations
  • Determining empirical formulas
  • Chemistry homework and exams

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