Last updated: 2026-06-16

Wind chill is the temperature that exposed skin actually feels in cold, windy weather. Wind strips away the thin layer of body-warmed air next to the skin and replaces it with cold air, speeding up heat loss, so a still −5 °C day feels much colder once the wind rises. This calculator turns an air temperature and wind speed into a "feels like" figure and a corresponding frostbite-risk category, using the formula adopted by the United States National Weather Service and Environment Canada in 2001.

How wind chill is calculated

The North American wind chill formula takes the air temperature $T$ in degrees Fahrenheit and the wind speed $V$ in miles per hour:

The $V^{0.16}$ term reflects how the cooling effect grows quickly at first and then levels off — the difference between a calm day and a 20 km/h breeze matters far more than the difference between 40 and 60 km/h. The calculator accepts Celsius, Fahrenheit, or Kelvin and any common wind-speed unit, converting internally to the Fahrenheit and mile-per-hour values the formula expects.

Worked example

Take an air temperature of $-5\,^\circ\mathrm{C}$ (about $23\,^\circ\mathrm{F}$) with a $20\;\mathrm{km/h}$ wind (about $12.4\;\mathrm{mph}$). Substituting into the formula:

So the wind makes the air feel about $6.5\,^\circ\mathrm{C}$ colder than the thermometer reads.

Risk categories and limits

As the wind chill drops, the time it takes for frostbite to develop on exposed skin falls sharply — from tens of minutes near −28 °C to just a few minutes below −48 °C. The categories shown reflect those thresholds. The formula is defined for air temperatures at or below 10 °C (50 °F) and winds above roughly 4.8 km/h (3 mph), and it describes heat loss from skin in the shade; sun, wet clothing, and exertion all change the real figure. For the warm-weather counterpart, see the Heat Index Calculator calculator.