Weather Calculators

Weather calculators apply meteorological formulas to convert between units and to derive the values that describe how conditions actually feel or behave. They take measurable quantities such as air temperature, humidity and wind speed and return either an equivalent in another unit or a composite index that combines several factors.

Temperature-conversion tools translate readings among the Celsius, Fahrenheit and Kelvin scales using fixed linear relationships, a routine need because weather reports in different countries use different scales. Pressure-conversion calculators do the same for atmospheric pressure, which can be expressed in units such as hectopascals, millibars, inches of mercury or millimetres of mercury, all describing the weight of the air column above a location.

Wind chill calculators estimate the lower apparent temperature a person feels in cold, windy conditions, because moving air carries heat away from exposed skin faster than still air; the effect depends on both air temperature and wind speed and matters only when it is cold. The heat index works in the opposite direction, combining high temperature with high humidity to express how hot it feels, since humid air slows the evaporation of sweat and reduces the body's cooling. Wind-speed calculators may convert between units such as kilometres per hour, knots and the descriptive Beaufort scale, or estimate speed from other data. Each of these outputs rests on empirical formulas fitted to observed effects on the human body or the atmosphere.

Frequently asked questions

What is wind chill?

Wind chill is the lower temperature a person perceives in cold weather because wind removes body heat faster than still air; it depends on both the air temperature and the wind speed.

Why does humidity raise the heat index?

High humidity slows the evaporation of sweat, which is how the body sheds heat, so a humid hot day feels hotter than a dry one at the same temperature.

In what units is atmospheric pressure measured?

Common units include hectopascals or millibars, inches of mercury and millimetres of mercury, all of which represent the weight of the atmosphere above a point and can be converted between one another.