Humidity Ratio Calculator
Calculate humidity ratio with transparent engineering inputs and the displayed formula.
Run deterministic checks for missing or mixed units, physical bounds, detectable out-of-range values and formula applicability. This is not an engineering approval or a complete code/compliance check.
Export the current calculation inputs and outputs with formula, assumptions, confirmed source credits, automated verification status, tool version and timestamp.
PROFENG Pro unlocks calculation-record exports. The calculation itself remains free.
PROFENG provides this tool for engineering screening and educational use. Check the calculation basis, units, physical assumptions, applicable standards, safety factors, equipment data and project-specific requirements before design, procurement or operation.
Turn this result into a calculation record
Carry the tool context into the PROFENG calculation-check and record workspace without implying certification or engineering approval.
Why use this humidity ratio calculator?
Calculate humidity ratio with transparent engineering inputs and the displayed formula. The displayed relationship is w = 0.62198 Pv/(P−Pv).
What this calculation does
This calculator determines humidity ratio from dry-bulb temperature, relative humidity, barometric pressure. Use it for HVAC and building-services screening with transparent air, thermal or flow assumptions.
Formula and engineering variables
w = 0.62198 Pv/(P−Pv)
| Variable | Definition | Unit | Working guidance |
|---|---|---|---|
temp | Dry-bulb temperature | °C | Illustrative screening band: 0 to about 250 °C. This is not a design limit. |
rh | Relative humidity | % | Physical percentage range where applicable: 0–100%. |
pressure | Barometric pressure | kPa | Illustrative screening band: 0 to about 1,013.25 kPa. This is not a design limit. |
Ranges above are screening guidance or physical bounds where stated. They are not code limits or manufacturer ratings.
Calculated outputs
- Humidity ratio (kg/kg dry air): 0.62198*((rh/100)*(0.61078*Math.exp(17.2694*temp/(temp+237.3))))/(pressure-(rh/100)*(0.61078*Math.exp(17.2694*temp/(temp+237.3))))
Worked example
- Dry-bulb temperature (temp) = 25 °C
- Relative humidity (rh) = 60 %
- Barometric pressure (pressure) = 101.325 kPa
0.62198*(((60)/100)*(0.61078*Math.exp(17.2694*(25)/((25)+237.3))))/((101.325)-((60)/100)*(0.61078*Math.exp(17.2694*(25)/((25)+237.3)))) = 0.01189 kg/kg dry airHumidity ratio: 0.01189 kg/kg dry airAssumptions
- Air or fluid properties are represented by the entered values.
- The calculation represents steady operation unless the formula explicitly includes time.
- Room, duct or envelope geometry is idealized by the displayed relationship.
Limitations
- Detailed load calculations, diversity, controls, equipment curves, psychrometric state changes and local code requirements may require additional analysis.
- Final equipment selection should use manufacturer data and the applicable HVAC design method.
- Total pressure must exceed vapor partial pressure.
- The humidity-ratio relationship is psychrometric, but the exact saturation-pressure approximation embedded in this implementation requires separate confirmation.
- The displayed default values are a worked example only; replace them with traceable project or measurement data.
Formula source and acknowledgement
Source being confirmed. PROFENG has not yet approved a published source for this exact implementation, so no candidate book, paper or standard is displayed here.
Limits of use for this relationship
- Total pressure must exceed vapor partial pressure.
- The humidity-ratio relationship is psychrometric, but the exact saturation-pressure approximation embedded in this implementation requires separate confirmation.
Read the PROFENG methodology for formula sourcing and automated checks →
How to use it
Start with the inputs shown above, review the assumptions or options, then generate the result. Where the tool creates a file, keep the original until you have opened and checked the downloaded output.
Frequently asked questions
What does Humidity Ratio Calculator calculate?
This calculator determines humidity ratio from dry-bulb temperature, relative humidity, barometric pressure. Use it for HVAC and building-services screening with transparent air, thermal or flow assumptions.
What formula does Humidity Ratio Calculator use?
The calculator uses w = 0.62198 Pv/(P−Pv). Every input used by the implementation is listed in the variable table on this page.
How is the worked example for Humidity Ratio Calculator checked?
PROFENG substitutes the displayed default values into the implemented relationship and compares the result against automated verification cases where an independent verifier is available.
What assumptions matter most for Humidity Ratio Calculator?
Air or fluid properties are represented by the entered values. The calculation represents steady operation unless the formula explicitly includes time. Room, duct or envelope geometry is idealized by the displayed relationship.
Can I use this result for final design or procurement?
Use it as an engineering screening calculation. Final design, procurement, operation or compliance decisions require project-specific data and the applicable engineering method, standard or manufacturer information.
QA, changelog and corrections
Last QA update: 30 September 2026.
Automated verification passed – 30 September 2026 – six numerical cases checked, with dimensional checks, independent cross-checks for calculators, and unit round-trip checks for converters where applicable.
Changelog
30 September 2026 – source/indexation status, metadata and correction pathway reviewed. Engineering tools display the automated verification label only when they are inside the passing Part 3 verification scope.