O₂ gas concentration

Oxygen PPM to mg/L Calculator

Convert oxygen in a gas mixture from ppm by volume to mass concentration at the selected temperature and pressure.

Formula mg/L = ppmv × 31.9988 × P ÷ (R × T) × 0.001

Live conversion

Oxygen PPM to mg/L Calculator

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Concentration — mg/L
Concentration — mg/m³

Results assume non-negative inputs and the unit basis shown.
Conversion basis

The formula behind the result

mg/L = ppmv × 31.9988 × P ÷ (R × T) × 0.001

This calculator is for oxygen in a gas. Dissolved oxygen in water uses a different measurement basis.

Converting gaseous oxygen ppm

Oxygen ppmv describes the fraction of oxygen molecules in a gas mixture. The ideal gas law converts that mole fraction into moles per liter, and oxygen's molar mass converts moles into milligrams.

Temperature and absolute pressure are required because gas density changes with both conditions.

Do not confuse gas oxygen with dissolved oxygen

Oxygen in air may be reported in ppmv or percent by volume. Dissolved oxygen meters usually report the mass concentration already in mg/L or a saturation percentage.

This gas-phase calculator does not model oxygen solubility, salinity, or water saturation.

Quick reference

Conversion examples

Input Conditions Result
1,000 ppmv 25 °C, 1 atm 1.308 mg/L
20,900 ppmv 25 °C, 1 atm 27.34 mg/L
209,000 ppmv 25 °C, 1 atm 273.4 mg/L
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Convert gas ppmv to mg/L with custom molar mass, temperature, and pressure using the ideal gas law.

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Frequently Asked Questions

How many mg/L is 1,000 ppm oxygen gas?
At 25 °C and 1 atm, 1,000 ppmv oxygen is approximately 1.308 mg/L of gas.
Can I use this for dissolved oxygen?
No. It converts gas-phase ppmv. Dissolved oxygen is governed by solubility and is usually measured directly in mg/L.
How do I convert oxygen percent to ppm?
Multiply percent by 10,000. For example, 20.9% is 209,000 ppmv.