Dew Point Calculator
You enter T and RH — no live weather feed. Click any i for detail.
Air
Units
i
Units
Temperature unit for both the input and the dew-point result. |
|
|---|---|
Air temperature
i
Temp
Dry-bulb temperature. |
|
Relative humidity (%)
i
RH
0–100. From a hygrometer, not a forecast app unless you type that number in. |
How to use this calculator
- Pick °F or °C.
- Enter air temperature.
- Enter RH.
- Read dew point. CFM / bath exhaust is a different job.
Results explained
Magnus-Tetens: γ = ln(RH/100) + (17.625 T) / (243.04 + T) with T in °C, then Td = 243.04 γ / (17.625 − γ).
Quick reference: dew point
When dew point approaches room temperature, surfaces sweat.
| Item | Detail |
|---|---|
| 70°F / 50% RH | Dew point in the 50s °F |
| Magnus a, b | 17.625 and 243.04 |
| Live METAR | Not fetched |
| Ventilation CFM | CFM calculator |
Wet-bulb and heat index are not this page.
How the estimate is built
Magnus-Tetens dew point from T and RH.
Example scenario
70°F at 50% RH → dew point about 50.5°F.
FAQ
Does this pull weather?
No. Type T and RH.
Frost point?
Same idea below freezing; this is still the Magnus sketch.
Indoor condensation?
Compare dew point to the coldest surface, not just the thermostat.