How do I calculate molar mass from a chemical formula?

Multiply each element's atomic mass by its atom count in the formula, then add all contributions.

What units are used for molar mass?

Molar mass is expressed as grams per mole (g/mol).

Accurate molar mass data for homework, exams & labs

Molar Mass Calculator, Formula & Compound List

What is Molar Mass?

Molar mass is the mass of one mole of a substance. It is expressed in grams per mole (g/mol).

It acts as a conversion factor between grams and moles, allowing you to convert between the amount of a substance and its mass.

How to use this calculator

Enter a formula (H₂O) or a compound name (for example water or oxygen).
While typing a name, matching compounds appear in a list under the field (scroll if the list is long). On phones and tablets, close it with the X or by choosing a compound. On desktop, it also closes when you click elsewhere on the page.
Press Calculate or choose a quick example.
Read the final answer in g/mol and element-by-element breakdown.

Quick examples:H₂O NaCl CO₂ H₂SO₄ C₂H₆O C₆H₆

Enter a valid formula or compound name (for example H₂SO₄ or Ca(OH)₂).

For instant numbers, use the calculator above or practice with the Molar Mass Practice Worksheet.

Calculate molar mass quickly, review the element-by-element breakdown, and open compound pages for worked examples.

How to Calculate Molar Mass

1. Identify elements and subscripts

Read the formula and list each element with its atom count from subscripts and parentheses.

2. Find atomic masses

Use the periodic table for element atomic masses (amu) in the formula.

3. Multiply by atom counts

For each element, multiply atomic mass by the number of atoms of that element.

4. Sum to total molar mass

Add all contributions. Report the final value in g/mol (grams per mole).

Molar Mass Formula

Molar mass is calculated by adding the atomic masses of all atoms in a compound.

M = Σ (atomic mass × number of atoms)

CO₂ → (1 × 12.01) + (2 × 16.00)

Ca(OH)₂ → (1 × Ca) + (2 × O) + (2 × H)

Parentheses indicate that all atoms inside the group are multiplied by the subscript outside.

How can I find the molar mass of an element?

Find the element's atomic mass on the periodic table. That value is the molar mass in g/mol. For example, carbon has an atomic mass of 12.01, so its molar mass is 12.01 g/mol.

Remember the seven diatomic elements in their natural form: H₂, N₂, O₂, F₂, Cl₂, Br₂, and I₂.

How can I find the molar mass of a chemical compound?

Add the masses of all atoms in the formula. Multiply each element's atomic mass by its atom count, including any counts affected by subscripts and parentheses.

Example: NaCl → (1 × 22.99) + (1 × 35.45) = 58.44 g/mol. Example: FeCl₂ → (1 × 55.85) + (2 × 35.45) = 126.75 g/mol.

For grouped formulas such as Zn(NO₃)₂, multiply atoms inside parentheses by the outside subscript before adding each element's total mass.

Examples

Common Mistakes

Forgetting or misreading subscripts (for example H₂O vs H₂O₂).
Using wrong or rounded-too-early atomic masses before the final sum.
Unit confusion: molar mass belongs in g/mol; watch mass vs moles in word problems.

Quick Reference

Molar mass vs molecular weight

In classroom chemistry they are often used the same way; molar mass is the standard term for values in g/mol.

Units of molar mass

Always g/mol (grams per mole) for molar mass in this site's tables and calculator output.

How to find molar mass quickly

List each element, multiply atomic mass by atom count, add once at the end—or enter the formula in the calculator.

Common Molar Mass Reference Chart (All Compounds)

Filter by

#	Compound	Formula	Molar mass
1	Water	H₂O	18.02 g/mol
2	Carbon Dioxide	CO₂	44.01 g/mol
3	Carbon Monoxide	CO	28.01 g/mol
4	Oxygen	O₂	32.00 g/mol
5	Ozone	O₃	48.00 g/mol
6	Nitrogen	N₂	28.01 g/mol
7	Nitric Oxide	NO	30.01 g/mol
8	Nitrogen Dioxide	NO₂	46.01 g/mol
9	Nitrous Oxide	N₂O	44.01 g/mol
10	Sulfur Dioxide	SO₂	64.06 g/mol
11	Sulfur Trioxide	SO₃	80.06 g/mol
12	Chlorine	Cl₂	70.90 g/mol
13	Hydrogen	H₂	2.02 g/mol
14	Ammonia	NH₃	17.03 g/mol
15	Hydrogen Sulfide	H₂S	34.08 g/mol
16	Hydrofluoric Acid	HF	20.01 g/mol
17	Hydrochloric Acid	HCl	36.46 g/mol
18	Hydrobromic Acid	HBr	80.91 g/mol
19	Hydroiodic Acid	HI	127.91 g/mol
20	Nitric Acid	HNO₃	63.01 g/mol
21	Sulfuric Acid	H₂SO₄	98.07 g/mol
22	Sulfurous Acid	H₂SO₃	82.07 g/mol
23	Phosphoric Acid	H₃PO₄	97.99 g/mol
24	Carbonic Acid	H₂CO₃	62.02 g/mol
25	Acetic Acid	C₂H₄O₂	60.05 g/mol
26	Formic Acid	HCOOH	46.02 g/mol
27	Sodium Hydroxide	NaOH	40.00 g/mol
28	Potassium Hydroxide	KOH	56.11 g/mol
29	Calcium Hydroxide	Ca(OH)₂	74.09 g/mol
30	Magnesium Hydroxide	Mg(OH)₂	58.32 g/mol
31	Sodium Chloride	NaCl	58.44 g/mol
32	Potassium Chloride	KCl	74.55 g/mol
33	Calcium Chloride	CaCl₂	110.98 g/mol
34	Magnesium Chloride	MgCl₂	95.21 g/mol
35	Sodium Carbonate	Na₂CO₃	105.99 g/mol
36	Sodium Bicarbonate	NaHCO₃	84.01 g/mol
37	Potassium Carbonate	K₂CO₃	138.20 g/mol
38	Calcium Carbonate	CaCO₃	100.09 g/mol
39	Sodium Sulfate	Na₂SO₄	142.04 g/mol
40	Potassium Sulfate	K₂SO₄	174.25 g/mol
41	Calcium Sulfate	CaSO₄	136.13 g/mol
42	Copper(II) Sulfate	CuSO₄	159.60 g/mol
43	Silver Nitrate	AgNO₃	169.87 g/mol
44	Sodium Nitrate	NaNO₃	84.99 g/mol
45	Potassium Nitrate	KNO₃	101.10 g/mol
46	Benzene	C₆H₆	78.11 g/mol
47	Toluene	C₇H₈	92.14 g/mol
48	Methanol	CH₃OH	32.04 g/mol
49	Ethanol	C₂H₆O	46.07 g/mol
50	Propanol	C₃H₈O	60.10 g/mol
51	Acetone	C₃H₆O	58.08 g/mol
52	Glucose	C₆H₁₂O₆	180.16 g/mol
53	Sucrose	C₁₂H₂₂O₁₁	342.30 g/mol
54	Styrene	C₈H₈	104.15 g/mol
55	Propionic Acid	C₃H₆O₂	74.08 g/mol
56	Methane	CH₄	16.04 g/mol
57	Ethane	C₂H₆	30.07 g/mol
58	Propane	C₃H₈	44.10 g/mol
59	Butane	C₄H₁₀	58.12 g/mol
60	Pentane	C₅H₁₂	72.15 g/mol
61	Hexane	C₆H₁₄	86.18 g/mol
62	Heptane	C₇H₁₆	100.20 g/mol
63	Octane	C₈H₁₈	114.23 g/mol
64	Nonane	C₉H₂₀	128.26 g/mol
65	Decane	C₁₀H₂₂	142.29 g/mol
66	Undecane	C₁₁H₂₄	156.31 g/mol
67	Dodecane	C₁₂H₂₆	170.34 g/mol
68	Tridecane	C₁₃H₂₈	184.37 g/mol
69	Tetradecane	C₁₄H₃₀	198.39 g/mol
70	Pentadecane	C₁₅H₃₂	212.42 g/mol
71	Hexadecane	C₁₆H₃₄	226.45 g/mol
72	Heptadecane	C₁₇H₃₆	240.47 g/mol
73	Octadecane	C₁₈H₃₈	254.50 g/mol
74	Nonadecane	C₁₉H₄₀	268.53 g/mol
75	Eicosane	C₂₀H₄₂	282.56 g/mol
76	Heneicosane	C₂₁H₄₄	296.58 g/mol
77	Docosane	C₂₂H₄₆	310.61 g/mol
78	Tricosane	C₂₃H₄₈	324.64 g/mol
79	Tetracosane	C₂₄H₅₀	338.66 g/mol
80	Pentacosane	C₂₅H₅₂	352.69 g/mol

509 compounds shown

How to write formulas (best format)

Use correct element symbols: one capital + optional lowercase (e.g. Na, Cl, Mg).
Put subscripts as digits after each symbol or group, e.g. H₂SO₄, Mg(OH)₂.
Parentheses group atoms that repeat together, e.g. Ca(OH)₂ (the digit after the closing parenthesis multiplies the whole group).

Featured compounds

Why Molar Mass Matters

Students use molar mass to convert grams to moles in exam questions.

Lab work uses it to measure exact reactant amounts for accurate results.

It also helps check reaction balance and reduce calculation mistakes.

How Molar Mass is Used in Real Life

In chemistry labs, students use molar mass to decide exact sample quantities before reactions start. For example, preparing solutions for Sodium Chloride (NaCl) and Sulfuric Acid (H₂SO₄) always depends on molar-mass accuracy.

In medicine and industry, measured compounds are converted between grams and moles to keep dosage and production consistent. That is why molar mass is treated as a core skill, not just an exam topic.

The lightest possible chemical that one can have under normal conditions is hydrogen gas, or H₂. There is no limit to how heavy a chemical compound can be - it is not uncommon for macromolecules (large organic or bioorganic compounds such as DNA) to weigh thousands of grams per mole.

Beginner Chemistry Guide

New to molar mass? Read the short definition, work through the step-by-step guide, then try Water (H₂O), Carbon dioxide (CO₂), or Sodium chloride (NaCl) from the chart above.

Popular molar mass lookup pages & formulas

FAQ

What is a molar mass calculator used for?

A molar mass calculator helps convert a chemical formula into grams per mole using atomic mass values.

Are these values useful for stoichiometry?

Yes. Molar masses are foundational for stoichiometric conversions between grams and moles.

Can I navigate between related compounds easily?

Yes. Every compound page includes related compounds, same-element links, and category clusters.