Example preset
Select a preset to fill the inputs and show a reference result immediately.
Inputs
Results
Formula details appear after calculation.
Assumptions and cautions
Tool assumptions (ideal gas and ppm definitions)
- 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. It converts ppm/ppb to mole fraction, converts that to molar concentration, and then converts to mass concentration using molecular weight.
Formula (ppm→mg/m³): C = ppm × P × MW / (R × T) × 10^-3
At the same ppm value, a higher temperature T lowers mg/m³, while a higher pressure P raises mg/m³. Include the temperature, pressure, and molecular weight you used whenever you report the converted value.
Use this page for gas-phase environmental or industrial calculations. Liquid ppm is usually a mass ratio such as mg/L and should not be converted with this gas formula.
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 calculator does not apply a humidity correction. If water vapor affects your use case, document whether the value is on a dry or wet basis and verify the result against the relevant 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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