Free dew point calculator with a comfort scale. Convert temperature and humidity to the dew point and see how dry, sticky, or oppressive the air feels.
You might also find these calculators useful
Calculate dew point instantly with our free calculator. Enter temperature and relative humidity to find the condensation temperature. Ideal for HVAC, compressed air systems, astronomy, agriculture, and building moisture control.
Dew point is the temperature to which air must cool for water vapor to condense into dew, fog, or clouds. It measures the ABSOLUTE amount of moisture in the air, so it is the single best gauge of how muggy the air feels. Meteorologists rank comfort by dew point: below 55°F (13°C) feels dry, 55–60°F is comfortable, 60–65°F turns sticky, 65–70°F is uncomfortable, and above 70°F (21°C) is oppressive. Unlike relative humidity — which rises and falls as the same air cools and warms through the day — the dew point barely changes, which is why forecasters quote it instead of RH.
Magnus Formula (Alduchov–Eskridge)
Controlling dew point in pneumatic systems prevents corrosion, freezing, and damage to valves and cylinders.
Astronomers calculate dew point to prevent condensation on lenses and mirrors during nighttime observations.
Monitoring dew point helps prevent fungal diseases and plan irrigation efficiently.
Designing systems that keep surfaces above dew point prevents mold and structural damage.
Predicting fog formation, carburetor icing, and visibility conditions for safe flights.
Applying paint when the surface is at least 3°C above dew point ensures proper adhesion.
Dew point is the best indicator of how humid and uncomfortable the air feels.
When temperature approaches dew point, fog, dew, or precipitation may form.
Prevent condensation, mold, and moisture damage in buildings.
Most people are comfortable when the dew point is below 60°F (16°C). Below 55°F (13°C) the air feels crisp and dry. From 60–65°F it starts to feel sticky, 65–70°F is noticeably humid, and above 70°F (21°C) is oppressive. These bands are the US National Weather Service comfort convention and are what our comfort scale shows.
A dew point of 70°F (21°C) or higher is considered high — the air feels heavy, sweat cannot evaporate well, and heat becomes dangerous. Dew points near 75–80°F (24–27°C) occur in tropical and monsoon climates and feel miserable. The record dew points on Earth are around 90°F (32°C).
Dew point is calculated with the Magnus formula: Td = (b × γ) / (a − γ), where γ = ln(RH/100) + (a×T)/(b+T). This calculator uses the Alduchov–Eskridge coefficients a = 17.625 and b = 243.04°C, accurate to within 0.1°C. For example, at 25°C with 60% humidity, the dew point is about 16.7°C.
70% is relative humidity, not dew point. At 25°C with 70% humidity, the dew point is about 19°C, which is humid and uncomfortable. To convert humidity to dew point you also need the air temperature, because the same 70% RH means very different mugginess at 15°C than at 30°C.
In industrial compressed air systems, typical dew points vary: Class 1 (-70°C), Class 2 (-40°C), Class 3 (-20°C), Class 4 (+3°C). A low dew point prevents condensation and corrosion in pipes and pneumatic equipment.
Relative humidity is a percentage that changes with temperature — the same air can read 50% in the afternoon and 90% overnight as it cools. Dew point is a fixed temperature that directly tells you how much water is in the air, so it is the better mugginess gauge. To go the other way, use our relative humidity calculator.
No, dew point can never exceed ambient temperature. When they're equal (100% humidity), the air is saturated and fog, dew, or condensation forms. If the calculated dew point were higher, it means an error in the input data.
Astronomers calculate dew point to protect telescopes and optical equipment. If equipment temperature drops below the dew point, condensation forms on lenses and mirrors, ruining observations. That's why they use dew heaters.