Molar Mass Calculator
Free online molar mass calculator. Compute molecular weight from any chemical formula using the full periodic table of atomic masses. 100% client-side.
Loading tool...
What is Molar Mass Calculator?
A Molar Mass Calculator determines the molecular weight of a chemical compound from its formula. You enter a formula like H2O or C6H12O6, and the tool parses each element symbol, counts atoms (including those inside parentheses groups and after hydrate dots), looks up standard atomic masses from the full periodic table of all 118 elements, and sums them into a total molar mass in grams per mole. The result includes a detailed breakdown showing each element count, atomic mass, subtotal contribution, and mass percentage composition. All calculations run locally in your browser with no data upload.
Key Benefits
- Full periodic table: all 118 elements with IUPAC 2021 standard atomic weights
- Smart formula parser handles parentheses groups and hydrate dot notation
- Detailed mass percent composition for every element in the compound
- Element and total atom counts plus a sortable composition table
- 100% client-side and offline-capable - nothing leaves your device
Common Use Cases
- •Chemistry homework: verify molar mass for stoichiometry and limiting reagent problems
- •Lab preparation: calculate grams needed for a specific molar concentration solution
- •Mass percent analysis for unknown compound identification
- •Pharmaceutical and biochemistry: verify molecular weights of active ingredients
- •Educational reference: quickly look up any element atomic mass from the periodic table
How to Use the Molar Mass Calculator
- Enter your chemical formula: Type a formula like H2O, C6H12O6, or Ca(OH)2 in the input field. You can use parentheses for groups and dots for hydrates (CuSO4.5H2O).
- Use an example if needed: Click any example chip (H2O, C6H12O6, H2SO4, etc.) to quickly load a common formula and see how it works.
- Read the molar mass: The large result card shows the total molar mass in g/mol. Below it, quick stats show the number of distinct elements and total atoms.
- Review the composition table: The breakdown table lists each element with its symbol, name, count, atomic mass, subtotal, and mass percentage. Click Copy to save everything as text.
Key Features
- Full periodic table coverage: all 118 elements with IUPAC 2021 atomic weights
- Smart parser handles parentheses groups like Ca(OH)2 and Fe2(SO4)3
- Hydrate dot notation support: CuSO4.5H2O, Na2CO3.10H2O
- Mass percent composition breakdown for every element
- Element count, total atom count, and sortable composition table
- 100% client-side - no data uploaded, works offline
Frequently Asked Questions
What is molar mass and how is it calculated?
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in the chemical formula. For example, water (H2O) has a molar mass of 2 times 1.008 (hydrogen) plus 15.999 (oxygen) equals 18.015 g/mol. Each element atomic mass comes from the periodic table using IUPAC 2021 standard values.
How do I handle parentheses and hydrates in a formula?
Parentheses create a group that is multiplied by the number after it. For example, Ca(OH)2 means one calcium, two oxygens, and two hydrogens. Hydrate dots separate water molecules attached to a compound, so CuSO4.5H2O means copper sulfate with five water molecules. The calculator handles both automatically.
What is mass percent composition?
Mass percent shows what fraction of the total molar mass comes from each element. It is calculated by dividing an element total mass contribution by the compound total molar mass and multiplying by 100. For example, in H2O oxygen contributes about 88.8 percent of the mass while hydrogen contributes about 11.2 percent.
Why might my calculated molar mass differ slightly from a textbook?
Atomic masses are not exact integers because they are weighted averages of naturally occurring isotopes. Different sources may round to different decimal places. This calculator uses IUPAC 2021 standard atomic weights, which are the most widely accepted values. Differences of plus or minus 0.01 g/mol are normal and due to rounding.