Molecular Weight Calculator

Calculate molecular weight by summing atomic weights of constituent atoms. Use this free browser-based molecular weight calculator from XTRAW Tools.

Molecular Weight Calculator helps you calculate molecular weight by summing atomic weights of constituent atoms. Use this free browser-based calculator from XTRAW Tools to compare inputs, estimate results, and plan your next step.

How to Use the Molecular Weight Calculator

Enter the required calculator inputs shown in the form.
Review the molecular-weight, mass, yield, concentration, dilution, gas-law, or colligative-property assumptions.
Run the calculator, then adjust one input at a time to compare scenarios or check your estimate.

What This Calculator Helps With

Calculate molecular weight by summing atomic weights of constituent atoms. It is designed for students, teachers, chemistry learners, lab users, healthcare reference users, STEM tutors, and anyone working with chemistry formulas who want a fast browser-based estimate before relying on a textbook, lab software, chemistry reference, professional source, or specialist.

H atoms: 2 ×1.008
C atoms: 0 ×12.011
N atoms: 0 ×14.007
O atoms: 1 ×15.999
Na atoms: 0 ×22.990
Cl atoms: 0 ×35.453
Ca atoms: 0 ×40.078
S atoms: 0 ×32.065
P atoms: 0 ×30.974
K atoms: 0 ×39.098

Common Uses

People use this calculator when they need a quick way to estimate formula weight, molar mass, equivalent weight, or mole-particle relationships.

Math Solving: Solve chemistry, concentration, stoichiometry, yield, gas-law, molecular-weight, or solution equations from entered values.
Measurement: Measure molar mass, percent composition, yield, dilution, concentration, normality, particles, osmotic pressure, or boiling point changes.
Unit Conversion: Convert chemistry quantities such as moles, particles, grams, concentration, and related formula values.

Formula or Method

MW = Σ(nᵢ × atomic weightᵢ)

Example

Example inputs: H atoms: 2 ×1.008; C atoms: 0 ×12.011; N atoms: 0 ×14.007; O atoms: 1 ×15.999; Na atoms: 0 ×22.990; Cl atoms: 0 ×35.453; Ca atoms: 0 ×40.078; S atoms: 0 ×32.065; P atoms: 0 ×30.974; K atoms: 0 ×39.098

Example result: Using the default atoms, molecular weight is about 18.015 g/mol.

Related Tools

Molecular Weight Calculator FAQ

Is the Molecular Weight Calculator free?

Yes. This calculator is free to use on XTRAW Tools.

Do I need to create an account?

No. XTRAW tools are designed for browser-based use without requiring an account.

Are the results exact?

Results may be estimates depending on the inputs, formula, rounding, chemistry reference values, assumptions, or purpose of the calculator. Always verify important results before relying on them.

Disclaimer: This calculator is provided for general informational, educational, and convenience purposes only. It is not medical, laboratory, chemical handling, safety, legal, financial, academic, regulatory, or professional advice. Always verify important results with a qualified professional, instructor, chemist, lab supervisor, safety documentation, authoritative source, or appropriate specialist before making decisions.