Molecular Weight Calculator

Molecular Weight Calculator

Calculate molecular weights and element composition of chemical compounds. Perfect for chemistry students, researchers, and laboratory work.

Chemical Formula

Use element symbols (H, O, C, N, etc.) and numbers for subscripts

Common Molecules

About Molecular Weight Calculator

This calculator determines the molecular weight of chemical compounds by summing the atomic weights of all atoms in the formula. Molecular weight is essential for stoichiometry, solution preparation, and chemical analysis. Enter formulas using standard element symbols (H2O, CO2, C6H12O6).

About Molecular Weight Calculator

Our comprehensive molecular weight calculator helps chemistry students, researchers, and laboratory professionals determine the molecular weights of chemical compounds with precision. This essential tool provides accurate calculations for stoichiometry, solution preparation, and chemical analysis, supporting both educational and professional chemistry applications.

What It Calculates

  • Molecular Weight: Total mass of one mole of compound
  • Element Composition: Individual element weights and percentages
  • Atomic Counts: Number of each element in the formula
  • Weight Distribution: How mass is distributed among elements
  • Formula Validation: Checks for valid chemical formulas
  • Precise Calculations: Accurate to multiple decimal places

Molecular Weight Fundamentals

Definition
  • Molecular Weight: Sum of atomic weights in molecule
  • Units: Grams per mole (g/mol)
  • Calculation: Σ(atomic weight × number of atoms)
  • Significance: Mass of one mole of substance
  • Precision: Based on atomic mass units
  • Standardization: IUPAC recommended values
Applications
  • Stoichiometry: Chemical reaction calculations
  • Solution Preparation: Molarity and molality
  • Chemical Analysis: Quantitative measurements
  • Research: Laboratory calculations
  • Education: Chemistry learning and teaching
  • Industry: Chemical manufacturing

Understanding Your Results

Molecular Weight

Total compound mass

Element Symbol

Chemical element

Atomic Count

Number of atoms

Weight %

Mass percentage

How to Use

Enter the chemical formula using standard element symbols (e.g., H2O, CO2, C6H12O6). The calculator automatically parses the formula, calculates molecular weight, and provides detailed element composition breakdown. Use common molecule buttons for quick examples, or enter custom formulas for specific compounds.

Chemical Formula Rules

Element Symbols:

  • Use standard periodic table symbols
  • First letter capitalized, second lowercase
  • Examples: H, He, Fe, Cu, Au
  • No spaces between elements
  • Subscripts for atom counts
  • Parentheses for complex groups

Formula Examples:

  • H2O (water): 2 hydrogen, 1 oxygen
  • CO2 (carbon dioxide): 1 carbon, 2 oxygen
  • C6H12O6 (glucose): 6 carbon, 12 hydrogen, 6 oxygen
  • Ca(OH)2 (calcium hydroxide)
  • Fe2O3 (iron oxide): 2 iron, 3 oxygen
  • H2SO4 (sulfuric acid)

Common Chemical Compounds

Inorganic Compounds
  • Water (H2O): 18.015 g/mol
  • Carbon Dioxide (CO2): 44.009 g/mol
  • Sodium Chloride (NaCl): 58.443 g/mol
  • Calcium Carbonate (CaCO3): 100.086 g/mol
  • Sulfuric Acid (H2SO4): 98.078 g/mol
  • Ammonia (NH3): 17.031 g/mol
Organic Compounds
  • Glucose (C6H12O6): 180.156 g/mol
  • Ethanol (C2H5OH): 46.068 g/mol
  • Methane (CH4): 16.043 g/mol
  • Benzene (C6H6): 78.114 g/mol
  • Acetic Acid (CH3COOH): 60.052 g/mol
  • Urea (CO(NH2)2): 60.056 g/mol

Stoichiometry Applications

  • Balancing Equations: Determine reactant/product ratios
  • Limiting Reagents: Calculate theoretical yields
  • Solution Preparation: Make solutions of known concentration
  • Gas Laws: Relate moles to volume and pressure
  • Thermochemistry: Calculate heat of reactions
  • Electrochemistry: Determine electron transfer

Laboratory Calculations

Solution Preparation
  • Molarity (M): Moles per liter of solution
  • Molality (m): Moles per kilogram of solvent
  • Normality (N): Equivalents per liter
  • Weight Percent: Mass of solute per 100g solution
  • Parts Per Million: Mass ratio calculations
  • Dilution Series: Concentration adjustments
Analytical Chemistry
  • Titration Calculations: Determine concentrations
  • Gravimetric Analysis: Mass-based measurements
  • Spectrophotometry: Concentration from absorbance
  • Chromatography: Peak area to concentration
  • Electrochemistry: Current to concentration
  • Quality Control: Standard preparation

Precision and Accuracy

  • Atomic Mass Units: Based on carbon-12 standard
  • Isotopic Composition: Natural abundance considered
  • Significant Figures: Appropriate precision maintained
  • Rounding Rules: Follow standard conventions
  • Uncertainty: Consider measurement precision
  • Validation: Cross-check with literature values

Common Calculation Mistakes

  • Formula Errors: Incorrect element symbols or counts
  • Atomic Weight Errors: Using wrong periodic table values
  • Subscript Confusion: Misreading atom counts
  • Parentheses Errors: Incorrect group multiplication
  • Unit Confusion: Mixing grams and atomic mass units
  • Rounding Errors: Over-precision or under-precision

Advanced Applications

  • Polymer Chemistry: Calculate average molecular weights
  • Biochemistry: Protein and nucleic acid analysis
  • Pharmaceuticals: Drug formulation calculations
  • Environmental Chemistry: Pollutant concentration analysis
  • Materials Science: Compound stoichiometry
  • Forensic Chemistry: Evidence analysis and identification
Pro Tip

Always verify your chemical formulas before calculating molecular weights. Double-check element symbols, subscripts, and parentheses placement. For complex compounds, break down the formula into smaller parts and calculate step by step. Keep a reference of common molecular weights for quick verification, and remember that molecular weight is essential for accurate stoichiometric calculations in chemistry.