Wind Chill Calculator
Work out how cold it really feels. Enter the air temperature (°F or °C) and wind speed (mph, km/h, m/s, or knots) to get the wind chill from the official U.S. National Weather Service formula — plus how quickly frostbite becomes a risk on exposed skin.
The NWS formula applies at air temperatures of 50°F (10°C) or below with wind of at least 3 mph; in lighter wind the feels-like temperature is essentially the air temperature.
What wind chill is and why wind matters
Your body constantly warms a thin layer of air against your skin. Wind strips that layer away, so heat leaves your skin faster and it cools toward the air temperature sooner — the wind chill is the calm-air temperature that would remove heat at the same rate. It’s a heat-loss model for people (calibrated on skin, walking at 3 mph), which is why pipes, radiators, and cars can never be chilled below the actual air temperature, only cooled toward it faster.
The frostbite line applies the U.S. National Weather Service chart bands: near a wind chill of −19°F exposed skin can freeze in about 30 minutes, and at extreme values the window shrinks to 10 and then 5 minutes. The bands overlap slightly because stronger wind freezes skin faster at the same wind chill.
How it’s calculated
NWS/JAG-TI wind chill (2001): WC = 35.74 + 0.6215T − 35.75V0.16 + 0.4275TV0.16, with T in °F and V in mph. Metric inputs are converted first (1 mph = 1.609 km/h = 0.447 m/s; knots × 1.151 = mph). Valid for T ≤ 50°F and V ≥ 3 mph. Source: National Weather Service / NOAA wind chill chart.
Wind chill models heat loss from exposed human skin — actual frostbite onset varies with wind, moisture, circulation, and clothing. Treat the times as planning guidance, not a safety guarantee.
Frostbite time warnings (NWS chart)
| Wind chill | Frostbite on exposed skin |
|---|---|
| Above 32°F (0°C) | No frostbite from cold air alone; hypothermia still possible when wet or under-dressed |
| 32 to about −18°F | Generally takes more than 30 minutes (often 2+ hours near the milder end) |
| About −19 to −34°F | Possible in as little as 30 minutes |
| About −35 to −57°F | Possible in as little as 10 minutes |
| −58°F and below | Possible in as little as 5 minutes — stay indoors |
Band edges are approximate: on the official chart the time to frostbite also depends on wind speed itself (NOAA notes a −58°F chill means ≤10 minutes in a 5 mph wind but ≤5 minutes at 45 mph). Source: NOAA/NWS wind chill chart.
Worked example
At 5°F with a 20 mph wind, the wind chill is −15°F (−26°C) — the wind makes it feel about 20°F colder than the thermometer reads. That sits in the “more than 30 minutes” frostbite band, but barely: drop to 0°F in the same wind and the chill reaches −22°F, inside the 30-minute band. A metric check: −5°C with a 30 km/h wind feels like about −13°C (9°F).
Common mistakes
- Expecting wind chill above 50°F — the formula (and the concept) applies to cold weather only.
- Worrying about pipes or engines “freezing at the wind chill”: objects can’t cool below the actual air temperature.
- Ignoring wetness — damp skin or clothing loses heat far faster than the chart assumes.
- Entering wind in km/h while the unit is set to mph (a 30 km/h breeze is only 18.6 mph).
Where it is used
- Deciding whether it’s safe for kids to walk to school or wait for the bus.
- Planning winter runs, hikes, hunts, and job-site work with exposure limits.
- Setting outdoor-work rotation schedules in cold snaps.
- Understanding NWS Cold Weather Advisories, which are triggered by wind chill.
Frequently asked questions
What formula does this use?
The 2001 NWS/JAG-TI formula used on the official U.S. wind chill chart: WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16 (T in °F, V in mph). It replaced the harsher 1945 Siple–Passel version and models a human face in wind at walking speed.
Why does it only work below 50°F and above 3 mph wind?
That is the range the formula was calibrated for. Above 50°F wind has little chilling effect on skin, and below 3 mph the air layer against your skin barely moves — the calculator then reports the air temperature itself.
Can wind chill freeze my pipes or car?
No. Wind chill describes heat-loss rate from warm skin, not a lower temperature. Objects cool faster in wind but never below the actual air temperature — if it is 35°F with a −5°F chill, water will not freeze.
How fast does frostbite really happen?
On the NWS chart: around −19°F wind chill, exposed skin can freeze in about 30 minutes; around −35°F in about 10 minutes; near −58°F in about 5 minutes. Fingers, toes, ears, and nose go first — cover them and get inside if skin numbs or whitens.
Is wind chill the same as “feels like” temperature?
In winter, yes — weather apps show wind chill as the feels-like value when it is cold and windy. In hot weather the feels-like number switches to the heat index, which combines temperature and humidity instead.