Gas Concentration Converter
Convert gas concentrations between ppm, ppb, percent by volume, mg/m³ and µg/m³ using gas-specific molecular weight and adjustable temperature and pressure.
Enter concentration
Select a gas, input unit and reference conditions.
Converted values
All outputs use the same reference temperature and pressure.
Convert volume ratios and mass concentrations correctly
The calculator first normalizes the input to ppm, then uses the ideal gas law for mass/volume conversion.
Choose the gas
Molecular weight is required for ppm-to-mg/m³ conversion.
Set reference conditions
Temperature and absolute pressure change the amount of gas in one cubic meter.
Review all outputs
Compare ppm, ppb, %vol, mg/m³ and µg/m³ on one screen.
%vol = ppm ÷ 10,000mg/m³ = ppm × P × MW × 0.001 ÷ (R × T)ppm = mg/m³ × R × T ÷ (P × MW × 0.001)Related Gas Nose tools
Gas Concentration Converter FAQ
Why do ppm and mg/m³ require a gas selection?
ppm is a volume ratio, while mg/m³ is a mass concentration. Molecular weight is required to connect the two.
What reference conditions should I use?
Use the actual temperature and absolute pressure when known. Many occupational references use 25°C and 1 atmosphere.
Is percent by volume the same as percent LEL?
No. Percent by volume is an absolute gas concentration. Percent LEL depends on the gas-specific lower flammability limit.
Can this calculate liquid concentration?
No. This page is for gases and vapors under an ideal-gas approximation.