Enter the temperature and wind speed to see how cold it feels on bare skin, and how soon frostbite can set in.
The NWS wind chill formula
The National Weather Service and Environment Canada have used this formula since 2001. T is the air temperature in °F and V is the wind speed in mph:
Wind chill (°F) = 35.74 + 0.6215T − 35.75V0.16 + 0.4275T × V0.16
It's only defined for temperatures at or below 50 °F and wind speeds of at least 3 mph. Outside that range the wind doesn't add meaningful cooling, so the calculator says so instead of giving a number. Celsius and km/h are converted to °F and mph first.
Worked example
At 0 °F with a 15 mph wind, V0.16 = 150.16 = 1.543. So wind chill = 35.74 + 0 − 35.75 × 1.543 + 0 = −19.4 °F. The NWS chart rounds this to −19 °F and shades it in the 30-minute frostbite band; the model below puts it at about 22 minutes.
Frostbite times
The NWS chart shades three frostbite zones: 30 minutes, 10 minutes and 5 minutes of exposure before bare skin can freeze. The times come from a model of facial skin cooling (Tikuisis and Osczevski, 2003), which this calculator uses to place your conditions in a zone:
Minutes to frostbite = (−24.5 × (0.667 × V + 4.8) + 2111) × (−4.8 − T)−1.668 (V in km/h, T in °C)
It applies only below −4.8 °C (about 23 °F) and estimates the time for the most susceptible people, so treat it as a warning, not a guarantee. The NWS chart leaves conditions with a wind chill warmer than about −18 °F unshaded (for example 0 °F in a 5 or 10 mph wind), so Calcist shows those as "over 30 minutes" even where the model gives a little under 30.
Limitations
- It assumes no sunshine. Bright sun can make it feel 10 to 18 °F warmer, according to the NWS.
- It's modeled on bare skin of an adult's face, with wind measured at face height. Clothing and shelter change everything.
- Wind chill can't cool an object below the air temperature. A car radiator at 20 °F won't freeze unless the air is below freezing.
Sources
How we checked this
Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:
- 0 °F with a 15 mph wind feels like −19.4 °F (NWS chart: −19) ✓
- Same: frostbite possible in about 22 minutes (Tikuisis–Osczevski), NWS 30-minute band ✓
- 0 °F at 5 mph (−10.5 °F) is unshaded on the NWS chart: over 30 min ✓
- −20 °F at 20 mph (−48.2 °F): about 7 minutes, 10-minute band ✓
- Chart rounding uses a true minus sign: −19 °F ✓
- 20 °F with a 20 mph wind feels like 4.2 °F (NWS example: 4) ✓
- −10 °C with a 20 km/h wind feels like −17.8 °C ✓
- 60 °F is outside the wind chill range ✓
Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.
Questions people ask
What is the wind chill at 0 °F with a 15 mph wind?
−19 °F, according to the NWS chart (−19.4 °F unrounded). Bare skin can freeze in about 30 minutes.
At what wind chill does frostbite happen in 30 minutes?
Around −19 °F (−28 °C) for most wind speeds, as at 0 °F with a 15 mph wind. It depends on both the temperature and the wind, which is why the chart shows zones.
Does wind chill apply above 50 °F?
No. The NWS formula is only defined for temperatures of 50 °F or below and winds of 3 mph or more.
Can wind chill freeze water pipes?
Only if the air itself is below freezing. Wind makes things lose heat faster, but they can't get colder than the air.