To convert carbon dioxide (CO₂) from moles to grams, multiply the amount in moles by 44.009 g/mol. For example, 0.1 mol corresponds to approximately 4.4009 g. Choose mol, mmol or µmol to convert smaller amounts without moving decimal places yourself.
The molar mass comes from one carbon atom and two oxygen atoms: 12.011 + 2 × 15.999 = 44.009 g/mol, using CIAAW abridged standard atomic weights. These weights describe normal materials and have uncertainty because isotopic composition varies; 44.009 g/mol is an approximate molar mass, not an exact constant.
The result shows grams, milligrams and the calculation after converting your input to moles. This is an amount-to-mass conversion for the stated CO₂ composition. It does not calculate gas volume, purity corrections, collection losses or a laboratory preparation procedure.
The formula
n- Amount of CO₂ in moles, after applying the selected amount unit.
M- Approximate molar mass of CO₂: 44.009 g/mol.
m- Mass of CO₂, displayed in grams and milligrams.
How to use this calculator
- Enter the amount of carbon dioxide and select mol, mmol or µmol. For example, choose mmol when entering 250 millimoles.
- Read the amount converted to moles. A mmol input is divided by 1,000; a µmol input is divided by 1,000,000.
- Multiply that amount in moles by 44.009 g/mol. The result is the mass in grams; multiplying the gram result by 1,000 gives milligrams.
- Check the displayed calculation and round to the precision justified by your original amount and the approximate atomic weights. Copy result includes the inputs and calculation.
Worked examples
0.1 mole of CO₂ in grams
0.1 mol × 44.009 g/mol = 4.4009 g, or 4,400.9 mg. One mole gives 44.009 g and two moles give 88.018 g using the same approximate molar mass.
250 millimoles of CO₂ in grams
First convert the amount: 250 mmol ÷ 1,000 = 0.25 mol. Then 0.25 mol × 44.009 g/mol = 11.00225 g, or 11,002.25 mg. Entering 250 as mol would give a result 1,000 times larger, so check the unit.
One micromole of CO₂ in milligrams
1 µmol ÷ 1,000,000 = 0.000001 mol. Multiplying by 44.009 g/mol gives 0.000044009 g. In milligrams, that is 0.044009 mg.
Frequently asked questions
How many grams are in one mole of CO2?
Using the CIAAW abridged atomic weights shown here, one mole of CO₂ has an approximate mass of 44.009 g. The calculation is 12.011 + 2 × 15.999 = 44.009 g/mol.
How do I convert mmol or micromoles of CO2 to grams?
Select mmol or µmol in the amount-unit field. Divide millimoles by 1,000 or micromoles by 1,000,000 to obtain moles, then multiply by 44.009 g/mol. One mmol is 0.044009 g; one µmol is 0.000044009 g using this molar mass.
Why do some references use 44.01 or 44 g/mol?
Those are rounded versions of a molar mass near 44.009 g/mol. Different atomic-weight tables and rounding choices can change the final digits. Use the precision specified in your problem or supported by your measurements.
Does temperature or pressure change the moles-to-grams conversion?
For a fixed chemical and isotopic composition, the amount-to-mass conversion uses molar mass and does not require temperature or pressure. Converting an observed gas volume to moles is a different calculation that requires conditions and an appropriate gas model.
Does this account for impurities or an isotope-labeled sample?
No. It assumes CO₂ with the normal atomic-weight composition represented by the displayed CIAAW values. A mixture, purity correction or isotope-labeled sample needs the appropriate composition and molar mass.
How are results rounded and what are the limits?
Calculations use the stored value 44.009 g/mol and convert units before rounding the displayed values. The main result displays at most 10 significant digits, or 8 in scientific notation for very small values. These digits are not a claim of measurement accuracy. The supported amount is 0 through 10,000 mol, equivalent to 10,000,000 mmol or 10,000,000,000 µmol.
CO₂ molar mass and amount conversions
| Element | Atom count | Atomic weight used | Contribution (g/mol) |
|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 |
| Oxygen (O) | 2 | 15.999 | 31.998 |
| CO₂ total | 3 | — | 44.009 |
The molar mass is approximate. CIAAW lists abridged atomic weights of 12.011 ± 0.002 for carbon and 15.999 ± 0.001 for oxygen.
| Amount of CO₂ | Moles | Grams | Milligrams |
|---|---|---|---|
| 1 µmol | 0.000001 | 0.000044009 | 0.044009 |
| 1 mmol | 0.001 | 0.044009 | 44.009 |
| 100 mmol | 0.1 | 4.4009 | 4,400.9 |
| 250 mmol | 0.25 | 11.00225 | 11,002.25 |
| 1 mol | 1 | 44.009 | 44,009 |