Analyzers calculators

pH, conductivity, and gas concentration conversions.

Gas Concentration Converter (ppm ↔ mg/m³ ↔ %LEL)

Convert gas concentration units with molecular weight.

pH Electrode Slope & Nernst Calculator

Electrode efficiency and offset from two-point buffer calibration.

Compressed Air Dew Point Converter (Pressure ↔ Atmospheric)

Pressure dew point to atmospheric dew point, with ISO 8573-1 class.

Conductivity, TDS & Resistivity Converter with Temperature Compensation

µS/cm ↔ ppm ↔ MΩ·cm, compensated to 25 °C.

Combustion Excess Air & Efficiency Calculator (from O₂)

Excess air, lambda and stack loss from flue gas oxygen.

About analyzers calculations

Analytical instrumentation measures composition rather than physical state, and it comes with a vocabulary problem: the same concentration is expressed four different ways depending on who is asking. Parts per million and percent by volume are the same molecular scale at different magnification. Milligrams per cubic metre converts that to mass through molecular weight, and is the language of occupational exposure limits. Percent LEL rescales everything against flammability, and is the language of safety systems.

Those scales are not interchangeable, and confusing them has consequences. Hydrogen sulphide is lethal at concentrations barely visible on a flammability scale — a gas detector calibrated for explosion risk is not a toxicity monitor, however reassuring its display looks.

Reference conditions matter here as much as anywhere else in instrumentation: mass concentration at 0 °C differs from the same gas at 25 °C by about nine percent, and regulations state which basis they intend.

How these tools fit together

  1. Identify the gas and its properties. Molecular weight drives mass conversion; the lower explosive limit drives flammability scaling.
  2. Fix the reference conditions. Mass concentration depends on temperature and pressure basis, so match whatever the applicable regulation or datasheet specifies.
  3. Convert deliberately between scales. Move between ppm, percent volume, mass concentration and percent LEL knowing which question each one answers.
  4. Set alarm levels against the right hazard. Flammability and toxicity are separate risks requiring separate detection and separate thresholds.

Frequently asked questions

How do I convert ppm to mg/m³?

Multiply the ppm value by the molecular weight and divide by the molar volume — 24.45 litres per mole at 25 °C and one atmosphere. Carbon monoxide at 1 ppm is about 1.145 mg/m³.

What does percent LEL mean?

The percentage of the lower explosive limit, indicating how close an atmosphere is to the minimum flammable concentration. Since 100% LEL of methane equals 5% by volume, detectors typically alarm at 10 to 20% LEL, well below flammability.

All calculators are provided for reference and education. Verify independently before use in safety-critical work — see our disclaimer.