Wind chill and dew point are both weather numbers derived from air temperature, but they answer different cold-weather questions. Wind chill adds wind speed and tells you how cold the air feels to exposed skin. Dew point adds relative humidity and tells you the temperature at which the air becomes saturated — the number behind frost, dew, and condensation. One measures the felt cold, the other the moisture content.
What each calculator does
The wind chill calculator takes air temperature and wind speed, converts them exactly to Fahrenheit and miles per hour, and applies the NWS equation WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16. It returns a value only when the converted temperature is at or below 50°F and the converted wind speed is above 3 mph — exactly 50°F counts, exactly 3 mph does not. The result is a whole-degree Fahrenheit wind-chill temperature for people, based on the NWS model’s assumption of a 5-foot height adjustment and no sunshine effect; it does not mean an inanimate object cools below the actual air temperature.
The dew point calculator takes air temperature and relative humidity and applies the Magnus approximation with constants a = 17.27 and b = 237.7: gamma = aT/(b + T) + ln(RH/100), then Td = b × gamma / (a − gamma). The result is the dew point rounded to two decimals, in the selected unit plus Celsius. Because dew point tracks the actual water-vapor content, it changes less than relative humidity as temperature rises and falls, which is why forecasters use it to describe mugginess — and why it predicts whether a surface at a given temperature will collect condensation.
Side-by-side
| Wind chill calculator | Dew point calculator | |
|---|---|---|
| Inputs | Air temperature and wind speed | Air temperature and relative humidity |
| Additional driver | Wind speed | Moisture content |
| Primary output | Wind-chill temperature in whole degrees Fahrenheit | Dew point rounded to two decimals, in the selected unit plus Celsius |
| What the number means | How cold the air feels to exposed skin | The temperature at which the air becomes saturated at constant moisture |
| Applicability | Only at or below 50°F and above 3 mph wind | Any temperature/humidity pair; zero percent humidity makes the logarithm undefined |
| Formula basis | NWS wind-chill equation | Magnus approximation (a = 17.27, b = 237.7) |
| Typical uses | Cold-weather exposure planning, frostbite context | Frost and dew, condensation checks, mugginess, building moisture |
When to use which
Use the wind chill calculator when the question is cold exposure: how the wind changes the felt temperature on skin, and whether conditions warrant extra layers or shorter time outside. The NWS model is built for people and animals, and the calculator is explicit that it does not estimate individual frostbite time or medical outcomes.
Use the dew point calculator when the question is moisture: whether leaves will stay wet overnight, whether a window or basement wall will condense, or how much cooling a dehumidifier must overcome. In winter it earns its place too — a dew point below freezing means surfaces at that temperature can frost — and the page’s comfort rules of thumb (dry below about 50°F, oppressive in the low 70s) frame the warm-season use.
The two calculators complement each other on a cold, damp day: wind chill explains why it feels colder than the thermometer, while dew point explains whether the cold air is dry or near saturation. For the warm end of apparent temperature, the heat index calculator fills the same “feels like” role that wind chill plays in winter.
Limits and disclaimer
Both pages are educational only and are not medical advice. Wind chill applies only inside the NWS scope, assumes no sunshine effect, and applies to people and animals rather than inanimate objects. The dew point is a Magnus approximation, accurate enough for common weather and indoor conditions but not for precision psychrometrics, and the form accepts zero percent humidity even though the logarithm is undefined there — use a small positive value for extremely dry air. Comfort descriptions are rules of thumb, not official medical limits, and cold- or heat-illness risk depends on clothing, exertion, sun, wind, hydration, and access to shelter in addition to any index.