Humidity Dew Point
Calculator

Relative humidity is a percentage showing how close the air is to saturation at its current temperature, while dew point is an absolute temperature — the point at which air would become saturated if cooled. Dew point is a more consistent measure of how much moisture is actually in the air, independent of the current air temperature.

Relative humidity is temperature-dependent: warm air can hold far more moisture than cold air, so 50% relative humidity at 90°F contains much more actual water vapor, and feels muggier, than 50% relative humidity at 40°F. Dew point stays more consistent as a comfort indicator across temperatures.

Dew points below 55°F (13°C) generally feel comfortable, 55-65°F (13-18°C) starts to feel humid, and above 65°F (18°C) feels distinctly muggy or oppressive to most people, regardless of the actual air temperature that day.

It uses a standard meteorological approximation formula (commonly the Magnus formula) that relates air temperature and relative humidity to the saturation point, since dew point can't be measured as directly as temperature or humidity without specialized equipment.

High dew points slow evaporative cooling for both people and plants, increasing heat stress risk during physical work and raising the likelihood of fungal disease on plant foliage that stays wet longer in humid air, which is why many extension services issue dew-point-based disease warnings.