CO₂ PPM to mg/L Calculator
Convert gaseous carbon dioxide from ppmv to mg/L at your actual temperature and pressure using the ideal-gas relationship.
Live conversion
CO₂ PPM to mg/L Calculator
The formula behind the result
mg/L = ppmv × 44.0095 × P ÷ (R × T) × 0.001 This page treats ppm as ppm by volume in a gas. R = 0.082057366 L·atm·mol⁻¹·K⁻¹.
Why CO₂ needs temperature and pressure
Gas ppm is normally a volume or mole fraction. Converting it to a mass per gas volume requires the gas molar mass and the number of moles occupying one liter, which changes with absolute temperature and pressure.
At 25 °C and 1 atm, 420 ppmv CO₂ is about 0.756 mg/L of gas, or about 756 mg/m³.
Gas-phase versus dissolved CO₂
This calculator is for CO₂ in a gas mixture such as air or process gas. Dissolved CO₂ in water is a liquid concentration and cannot be inferred from gas ppm with this formula alone.
Gas-to-water equilibrium depends on temperature, pressure, pH, alkalinity, and Henry's law, so use a dissolved-CO₂ method for water samples.
Conversion examples
| Input | Conditions | Result |
|---|---|---|
| 420 ppmv | 25 °C, 1 atm | 0.7555 mg/L |
| 1,000 ppmv | 25 °C, 1 atm | 1.7988 mg/L |
| 5,000 ppmv | 20 °C, 1 atm | 9.148 mg/L |