Humidity ratio
w = 0.62198 Pv / (P - Pv)
Thermodynamics calculator
Humidity Ratio Calculator
Estimate water vapor mass per mass of dry air.
Calculator
Enter thermal values
Select units beside each input. Results update automatically.
Result
About this calculator
How it works
Humidity ratio is the mass of water vapor per mass of dry air. This uses a saturation-pressure approximation.
Formulas
Formulas used
Vapor pressure
Pv = RH x Psat / 100
Worked example
Example calculation
Humidity ratio
25 C, 50% RH, 101.325 kPa gives about 0.0099 kg/kg dry air
Guide
How to use this calculator
- Enter the known temperature, pressure, energy, humidity, or material values.
- Select units beside each input where unit menus are shown.
- Use the highlighted result for screening and verify assumptions before design use.
Reference
What the results mean
Humidity ratio
Water vapor mass per dry-air mass.
Vapor pressure
Partial pressure of water vapor in moist air.
Assumptions and limits
Before using the result
- Calculations use simplified ideal relations or common approximations for quick engineering checks.
- Real systems may require property tables, phase behavior, transient analysis, losses, and code or manufacturer data.
- Use verified data and qualified engineering judgement for final design or safety-critical work.
FAQ
Humidity Ratio Calculator questions
Are these results suitable for final thermodynamic design?
Use these tools for education, screening, and early checks. Final work should use verified properties, standards, operating limits, and qualified engineering review.
Why can real thermal systems differ from these calculations?
Real systems include losses, non-ideal properties, transient behavior, two-phase effects, humidity assumptions, heat leaks, and measurement uncertainty.
Can I use different units?
Yes. Select units beside inputs where menus are shown. Values are converted internally before solving.
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