Enter Inputs
Tip: If pressure is unknown, use local station pressure for best accuracy.
Example Data Table
| Dry-bulb | RH | Pressure | Humidity ratio (g/kg) |
|---|---|---|---|
| 25 °C | 50% | 101.325 kPa | ~9.88 |
| 30 °C | 60% | 101.325 kPa | ~16.0 |
| 18 °C | 40% | 90 kPa | ~6.0 |
Values are approximate and depend on the saturation pressure correlation.
Formula Used
The humidity ratio w (also called mixing ratio) relates water vapor to dry air:
- Pws(T): saturation vapor pressure at dry-bulb temperature
- Pw = RH × Pws: water vapor partial pressure
- w = 0.62198 × Pw / (P − Pw): humidity ratio (kg/kg dry air)
Advanced outputs include q = w/(1+w) (specific humidity), vapor density from the ideal gas law, and moist-air enthalpy using a common HVAC approximation.
How to Use This Calculator
- Enter dry-bulb temperature and choose °C or °F.
- Enter relative humidity as a percentage from 0 to 100.
- Enter barometric pressure and select its unit.
- Choose whether to show advanced outputs.
- Press Calculate to view results above the form.
- Use CSV for spreadsheets, or print to save a PDF.