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 sum using the listed atomic weights 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
Atomic-weight sum before rounding: 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. Using the listed, rounded standard atomic weights gives approximately 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
Use the listed, rounded standard atomic weights: 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 total using these atomic weights is approximately 44.009 g/mol, usually reported as 44.01 g/mol. One mole of CO₂ — 6.022 × 10²³ molecules, 3 atoms each — has approximately 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
Convert grams ↔ moles of CO₂ in the full calculator →
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 the listed, rounded standard atomic weights, the calculation 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.
Atomic weight reference
Calculations use the rounded standard atomic weights shown in the breakdown, not exact isotope masses. Natural isotope composition can vary, and some standard atomic weights are reported as intervals. See the CIAAW standard atomic weights for the reference values. Use your course’s table when its rounding differs.