Dew Point Calculator
Find the dew point from temperature and humidity, or the humidity from the dew point, plus wet bulb and humidity ratio.
- Relative humidity
- Wet bulb
- Vapor pressure
- Humidity ratio
- Absolute humidity
- Temperature minus dew point
- Feels
Readings
Items you add are saved in this browser.
| Place | Temp | RH | Dew Point | Grains/Lb. | Remove |
|---|
How to Calculate Dew Point
Dew point is the temperature at which air becomes saturated and water starts to condense. It's found from temperature and relative humidity with the Magnus formula, which is accurate to a few tenths of a degree in the ordinary range of weather.
Wet bulb temperature uses Stull's (2011) empirical formula, good to within about 1 °C for relative humidity between 5% and 99% and temperatures from −20 °C to 50 °C.
Worked Example
How Dew Point Feels
| Dew Point | Comfort |
|---|---|
| Below 50 °F (10 °C) | Dry, comfortable |
| 50–60 °F (10–16 °C) | Comfortable |
| 60–65 °F (16–18 °C) | Getting sticky |
| 65–70 °F (18–21 °C) | Humid, uncomfortable |
| Above 70 °F (21 °C) | Oppressive |
General comfort guide, similar to the one used by the National Weather Service.
Tips
Any surface colder than the dew point will sweat: cold water pipes, ducts in an attic, windows in winter. Keeping indoor dew point under about 55 °F in summer helps prevent mold. The Magnus constants used here are for water; over ice the numbers are slightly different.