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PPM to mg/L for Gas Calculator

Enter the gas molar mass and operating conditions to convert a ppm by volume reading into mg/L and mg/m³.

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

Live conversion

PPM to mg/L for Gas Calculator

Updates live
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 × molecular weight × P ÷ (R × T) × 0.001

Use absolute temperature in kelvin internally and pressure in atmospheres. The calculator converts the selected units automatically.

Gas ppm to mass concentration

For gases, ppm usually means ppm by volume, which is equivalent to a mole fraction for ideal mixtures. A molar mass is therefore required to turn that fraction into mass.

Temperature and pressure determine how many total gas molecules occupy each liter. Enter actual conditions when they are known rather than relying on a standard-condition shortcut.

Inputs you need

Use the molecular weight of the measured compound in grams per mole, not the average molecular weight of the carrier gas. Choose the temperature and absolute pressure units that match the source data.

If a monitoring standard specifies normal or standard conditions, enter the exact temperature and pressure defined by that standard.

Quick reference

Conversion examples

Input Conditions Result
100 ppmv, MW 44.0095 25 °C, 1 atm 0.17988 mg/L
50 ppmv, MW 28.01 20 °C, 1 atm 0.05823 mg/L
10 ppmv, MW 64.066 0 °C, 1 atm 0.02858 mg/L
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Frequently Asked Questions

What molecular weight should I enter?
Enter the molar mass of the measured gas compound in g/mol.
Should pressure be absolute or gauge pressure?
Use absolute pressure. Convert gauge pressure to absolute pressure before entering it.
Can ppm always be converted to mg/L?
Only when the ppm basis and physical conditions are known. This calculator assumes gas-phase ppm by volume and ideal-gas behavior.