Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Actual vapor pressure (hPa)

Required number input.

Saturation vapor pressure (hPa)

Required number input.

Compute relative humidity as the ratio of actual to saturation vapor pressure. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Relative humidity (%)

The resulting relative humidity returned as a number.

• Humidity and wet-bulb relationships depend on pressure, temperature scales, phase conventions, ventilation, and the selected saturation-vapor-pressure correlation. Local measurements and full psychrometric methods are needed for precision work.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Vapor Density Relative to Air Calculator

  Compute vapor density relative to air as the ratio of molar masses M(gas)/28.96.

• Vapor Density Relative to H2 Calculator

  Compute vapor density relative to hydrogen as the ratio of molar masses M(gas)/M(H₂).

• Vapor Pressure Lowering

  Estimate relative vapor pressure lowering from the solute mole fraction.