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chemistry

Molar Mass Calculator

Calculate the molar mass of a compound by summing the atomic masses of its constituent elements.

Reviewed by Christopher FloiedPublished Updated

This free online molar mass calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.

Atomic mass of the first element (e.g., C = 12.011).

Number of atoms of element 1 in the formula.

Atomic mass of the second element (e.g., H = 1.008).

Optional third element (e.g., O = 15.999). Enter 0 if not needed.

Results

Molar Mass

84.162 g/mol

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the Molar Mass Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The Molar Mass Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

When to Use This Calculator

  • •Use the Molar Mass Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
  • •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
  • •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
  • •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.

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About Molar Mass Calculator

The molar mass calculator computes the molecular weight of a chemical compound by summing the atomic masses of each element multiplied by the number of atoms of that element in the molecular formula. Molar mass is expressed in grams per mole (g/mol) and is essential for converting between mass and moles in virtually every chemistry calculation. This calculator supports up to three elements, covering a wide range of common molecules. For more complex compounds, simply break the calculation into groups.

The Math Behind It

The molar mass of a compound equals the sum of the molar masses of all atoms in its formula. Each element's molar mass is its standard atomic weight from the periodic table, which is a weighted average of naturally occurring isotope masses. For example, glucose (C₆H₁₂O₆) has a molar mass of 6(12.011) + 12(1.008) + 6(15.999) = 72.066 + 12.096 + 95.994 = 180.156 g/mol. Molar mass connects the atomic scale (individual molecules, measured in daltons or amu) to the laboratory scale (bulk samples, measured in grams). Knowing the molar mass is a prerequisite for calculating molarity, theoretical yield, percent composition, empirical formulas, and virtually all quantitative chemistry problems.

Formula Reference

Molar Mass Calculation

MW = Σ (atomic mass × count)

Variables: MW = molar mass (g/mol); sum over all elements in the molecular formula

Worked Examples

Example 1: Glucose (C₆H₁₂O₆)

C: 12.011 g/mol × 6; H: 1.008 × 12; O: 15.999 × 6.

Step 1:C contribution = 12.011 × 6 = 72.066.
Step 2:H contribution = 1.008 × 12 = 12.096.
Step 3:O contribution = 15.999 × 6 = 95.994.
Step 4:Total = 72.066 + 12.096 + 95.994 = 180.156 g/mol.

The molar mass of glucose is 180.156 g/mol.

Common Mistakes & Tips

  • !Using the mass number of a single isotope instead of the standard atomic weight.
  • !Miscounting atoms, especially in formulas with parentheses like Ca(OH)₂.
  • !Confusing molar mass (g/mol) with density (g/mL).

Related Concepts

Grams to Moles

Use molar mass to convert between grams and moles.

Molarity

Molar mass is needed to prepare solutions of known molarity from a weighed amount of solid.

Used in These Calculators

Calculators that build on or apply the concepts from this page:

Grams to Moles Calculator

Frequently Asked Questions

Where do I find atomic masses?

Standard atomic weights are published by IUPAC and listed on every periodic table. For precise work, use the most recent IUPAC values.

What about hydrated salts?

Include the water of crystallization. For CuSO₄·5H₂O, add the molar mass of CuSO₄ (159.6) plus 5 × 18.015 (90.1) = 249.7 g/mol.

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