Online Tool Store
Psychrometric Calculator
Calculate relative humidity, dew point, wet bulb temperature, and absolute moisture content from any two known air properties.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Math & Science
Psychrometric Calculator
Frontend preview — no upload or external service.
Air properties
24 °C at 65% RH: dew point 17.1 °C, wet bulb 19.5 °C, absolute humidity 12.2 g/kg. Any surface below 17.1 °C in this air will condense.
How the Psychrometric Calculator works
- Enter two known properties — dry bulb plus relative humidity is the usual pair.
- Read the dew point, which is the temperature at which condensation begins on any surface.
- Use absolute humidity when comparing air at different temperatures, since relative humidity alone is misleading across a temperature change.
The method
Relative humidity is moisture relative to what the air can hold at that temperature, so it changes when the temperature changes even though the moisture does not.
dew point is the temperature at which the air reaches saturation with its current moisture content
Air at 24 °C and 65% RH holds 12.2 g/kg. Cool it to 17.1 °C and that same moisture is 100% RH — which is why cold surfaces sweat.
FAQ
Why does relative humidity mislead?
Because it depends on temperature as well as moisture. Air moved from a cold room to a warm one has the same moisture and a much lower relative humidity, which is why heated winter air feels dry without anything being removed.
What is dew point actually useful for?
Predicting condensation. Any surface colder than the dew point will collect moisture — which is the whole basis of insulation design, cold bridge analysis, and why a glass of iced water sweats.
Why does wet bulb temperature matter?
It sets the limit for evaporative cooling and, in extreme heat, for human survivability — sweat cannot cool you below the wet bulb temperature no matter how much you produce.
How we compare
| Feature | Online Tool Store | A graphing calculator | A stats package |
|---|---|---|---|
| Multiple properties from two inputs | ✓ | Chart reading | Yes |
| Altitude correction | ✓ | ✗ | ✓ |
| No psychrometric chart needed | ✓ | ✗ | ✗ |
| Works offline once loaded | ✓ | ✓ | ✗ |
Psychrometric Calculator leads with dew point, because condensation risk is the question most people are really asking when they measure humidity.