Wind Chill
This free wind chill calculator finds how cold it feels from air temperature and wind speed, using the US National Weather Service's official formula. Nothing you enter is sent anywhere or stored.
How to Use It
- Enter the air temperature.
- Enter the wind speed.
- The wind chill updates instantly, no submit button.
How It Works
Wind strips away the thin layer of air your skin has already warmed, forcing your body to keep giving up heat faster than it would in still air at the same temperature. The National Weather Service's formula models that extra heat loss directly from skin heat transfer data, combining air temperature and wind speed into a single "feels like" number.
Formula
wind chill = 35.74 + (0.6215 × T) − (35.75 × V^0.16) + (0.4275 × T × V^0.16)
A worked example: at 20°F with a 15 mph wind, the formula gives a wind chill of about 6.2°F, noticeably colder than the actual air temperature. At 0°F with a 10 mph wind, it drops further to about −15.9°F. Both results only apply within the formula's tested range, air temperature at or below 50°F and wind speed at or above 3 mph.
Everything runs client-side in your browser. Nothing you enter is sent anywhere or stored.
Frequently Asked Questions
What does wind chill actually measure?
Wind chill measures how cold exposed skin feels, not a change in the actual air temperature a thermometer reads. Moving air strips away the thin layer of air your skin has warmed, so heat leaves your skin faster in wind than it does on a calm day at the same temperature, and wind chill expresses that faster heat loss as an equivalent "feels like" temperature.
Why does wind chill only apply at 50°F and below, with wind of 3 mph or more?
The formula was developed and tested against skin heat loss data within that range, since wind chill is only a meaningful effect when it's genuinely cold and there's enough wind to matter. Above 50°F or below 3 mph, the formula's underlying model does not apply, so this calculator does not extrapolate a number outside the range it was built for.
Where do the formula's numbers come from?
This calculator uses the modern wind chill formula the US National Weather Service adopted in 2001, developed from controlled studies of how fast human skin actually loses heat in cold and wind. It replaced an older 1945 formula that overstated wind's cooling effect, since the original was based on how quickly water froze in a container, not real skin.
Can you give a real-world example?
A calm 20°F day and a windy 20°F day with a 15 mph wind feel very different, even though a thermometer reads the identical 20°F in both. The windy day has a wind chill of about 6°F, cold enough to noticeably increase the risk of frostbite on exposed skin within a shorter amount of time than the calm day would.