ppm/ppb ↔ mg/m³ conversion (gas)

Example preset

Once selected, the input field will be filled in and the result will be displayed immediately (reference example).

preset

Inputs

Concentration (ppm)

Gas (molecular weight)

*Molecular weight is a reference value. Strictly speaking, there are slight differences depending on the data source.

Temperature (°C)

pressure

Results

Conversion result

— mg/m³

expression (this condition)

Assumptions and precautions (prevention of misuse)

Assumptions of this tool (definition of ideal gas/ppm)

ppm/ppb is treated as a volume (= mole) mixing ratio (ideal gas, Z=1).
No humidity correction is performed (dry/wet differences are not taken into account).
At high pressures and concentrations, errors may increase due to non-ideality.

How to convert ppm to mg/m³

This tool uses the ideal gas equation PV=nRT use. Convert ppm/ppb to mole fraction, convert to molar concentration, and then convert to mass concentration using molecular weight.

Formula (ppm→mg/m³): C = ppm × P × MW / (R × T) × 10^-3

temperature T When ppm is the same, mg/m³ becomes smaller and the pressure P The higher the value, the larger the value. Be sure to include the temperature and pressure conditions you entered in the report.

Frequently asked questions

Which standard state does this use?

The calculator does not force a single standard state. It converts using the temperature and pressure you enter, and the presets are only shortcuts for common reporting conditions.

What if the gas is humid?

This MVP does not apply a humidity correction. If water vapor matters for your workflow, document the dry or wet basis separately and verify the result with your lab or regulatory method.

Is this the same as liquid ppm conversion?

No. This page assumes gas-phase volume mixing ratio, where ppm or ppb behaves like a mole fraction under the ideal-gas model. Liquid ppm is often treated as a mass ratio such as mg/L.

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