CO₂ Molar Mass
Carbon dioxide
The molar mass of CO₂ (carbon dioxide) is approximately 44.01 g/mol. Each molecule carries one carbon atom and two oxygen atoms, so the exact sum is 12.011 + (2 × 15.999) = 44.009 g/mol — about 27.3% carbon and 72.7% oxygen by mass.
Molar mass of CO₂
44.01 g/mol
Exact value from IUPAC standard atomic weights: 44.009 g/mol
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Looking for its bonding structure? See the CO₂ Lewis Structure →
| Formula | CO₂ |
|---|---|
| Molar Mass | 44.01 g/mol |
| Molecular Weight | 44.009 |
| Carbon Atoms | 1 |
| Oxygen Atoms | 2 |
| Total Atoms | 3 |
How to Calculate the Molar Mass of CO₂
The molar mass of CO₂ is the sum of one carbon atomic weight and two oxygen atomic weights. The IUPAC standard atomic weights give exactly 44.009 g/mol — rounded to 44.01 g/mol for classroom use.
CO₂
- Carbon: 1 × 12.011 = 12.011
- Oxygen: 2 × 15.999 = 31.998
12.011 + 31.998 = 44.009 g/mol
≈ 44.01 g/mol
Step 1 Read the chemical formula
CO₂ contains 1 carbon atom and 2 oxygen atoms. Subscripts count atoms, and a symbol without a subscript counts one.
Step 2 Find the atomic masses
Look up each element's IUPAC standard atomic weight on the periodic table: C = 12.011 and O = 15.999. Most atomic weights are not whole numbers — each one averages an element's naturally occurring isotopes.
Step 3 Multiply by the atom counts
Each element contributes its atomic weight once per atom: C: 1 × 12.011 = 12.011; O: 2 × 15.999 = 31.998.
Step 4 Add the contributions
12.011 + 31.998 = 44.009 g/mol. The IUPAC total is 44.009 g/mol, usually reported as 44.01 g/mol. One mole of CO₂ — 6.022 × 10²³ molecules, 3 atoms each — has exactly this mass in grams.
Elemental Composition of CO₂
Each element's share of the total mass of one mole of CO₂. One mole — about 44.01 g — contains 12.011 g of carbon and 31.998 g of oxygen, and every sample scales by the same ratio. Stated as percent composition, CO₂ is 27.29% carbon and 72.71% oxygen by mass.
| Element | Atoms | Atomic Weight | Mass Contribution | Mass % |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 27.29% |
| Oxygen (O) | 2 | 15.999 | 31.998 | 72.71% |
| Total | 3 | 44.009 | 100% |
What Is the Molecular Weight of CO₂?
For CO₂ the two terms describe the same number from two directions. The molar mass is the mass of one mole of CO₂ molecules: 44.01 g/mol. The molecular mass is the mass of one single CO₂ molecule: about 44.009 u (unified atomic mass units), also written 44.009 Da. The values are numerically identical because the mole is defined that way — 1 g/mol corresponds to 1 u per molecule.
You will also see "relative molecular mass of carbon dioxide", which is the same quantity compared against 1/12 of a carbon-12 atom, and reference tables such as NIST listing molecular weight 44.0095 — a slightly older atomic-weight set that rounds to the same classroom value. Whether a source says 44.009, 44.0095, or 44.01, it is the same quantity to three significant figures.
| Molar mass | 44.01 g/mol — the mass of one mole of CO₂ molecules |
|---|---|
| Molecular mass | ≈ 44.009 u (Da) — the mass of one single CO₂ molecule |
How Many Grams Are in One Mole of CO₂?
One mole of CO₂ has a mass of approximately 44.01 grams. That is the whole conversion — the molar mass is the conversion factor between moles and grams. Going the other way, divide by the same factor: 88.02 g of CO₂ is 88.02 ÷ 44.01 = 2 mol. Type an amount below to convert either way; the calculation uses 44.01 g/mol.
1 mol of CO₂ has a mass of 44.01 g
Need a full reaction calculation? Open the Stoichiometry Calculator →
CO₂ Formula Breakdown
CO₂
- C = Carbon × 1
- O = Oxygen × 2
- Total atoms = 3
The subscript ₂ applies only to the oxygen — carbon keeps its implied subscript of 1. Coefficients written in front of a formula (the 2 in 2CO₂) count separate units and do not change the molecule itself.
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Related Chemistry
- CO₂ Lewis StructureTwo C=O double bonds, 16 valence electrons, linear 180° geometry.
- Molar Mass CalculatorMolar mass, molecular weight, and composition for any formula.
- Stoichiometry CalculatorConvert between moles, mass, and reaction amounts.
- Empirical Formula CalculatorTurn percent composition into a formula.
- Chemical Equation BalancerBalance equations with coefficients and atom checks.
Frequently Asked Questions
What is the molar mass of CO₂?
Approximately 44.01 g/mol. Using IUPAC standard atomic weights, the exact value is 1 × 12.011 (carbon) + 2 × 15.999 (oxygen) = 44.009 g/mol, which rounds to 44.01 g/mol.
How do you calculate the molar mass of CO₂?
Add one carbon atomic mass to two oxygen atomic masses: 12.011 + (2 × 15.999) = 44.009 ≈ 44.01 g/mol. In general: read the subscripts in the formula, multiply each element's atomic weight by its atom count, then add the contributions.
What is the molecular weight of CO₂?
About 44.01 — molecular weight is numerically identical to molar mass. One CO₂ molecule has a molecular mass of roughly 44.009 u (Da); one mole of CO₂ weighs 44.009 g. Some reference tables, such as NIST, list 44.0095 because they use a slightly older atomic-weight set — all of these are the same value to three significant figures.
How many atoms are in CO₂?
Three in total: one carbon atom and two oxygen atoms in every CO₂ molecule.
How many grams are in one mole of CO₂?
About 44.01 grams. One mole contains 6.022 × 10²³ CO₂ molecules, and the molar mass converts that amount directly to mass: 1 mol × 44.01 g/mol = 44.01 g.
Does the coefficient in 2CO₂ change the molar mass?
No. The molar mass describes one CO₂ unit, so it stays 44.01 g/mol regardless of the coefficient. A coefficient counts how many units are present: 2CO₂ means two moles of CO₂, which have a total mass of 2 × 44.01 = 88.02 g. Do not confuse the coefficient with the subscript ₂, which is part of the formula itself and means two oxygen atoms per molecule.