Wind Chill Calculator
Enter the air temperature and the wind speed and get the wind chill — how cold it feels on exposed skin — with the frostbite risk level and the time exposed skin takes to freeze. It uses the 2001 wind chill formula shared by the US National Weather Service and the Meteorological Service of Canada, shows its working and its valid range, and prints a full chart. Runs entirely in your browser — free, no sign-up.
As measured at the standard 10 m (33 ft) anemometer height.
Results
6.2 °F
Wind chill (feels like)
-14.3
Same value in °C
13.8 °F
Feels colder than the air by
Moderate
Frostbite risk level
Time for exposed skin to freeze: Risk of frostbite and hypothermia after long exposure without adequate protection
Risk levels and frostbite times are those Environment and Climate Change Canada publishes. In sustained winds over 50 km/h (31 mph) frostbite can happen faster than shown, and the index assumes no sun on a clear night.
The working
- Converted: T = 20 °F (-6.67 °C) and V = 15 mph (24.14 km/h).
- where V^0.16 = 15^0.16 = 1.5423.
- WCT = 35.74 + 0.6215 T − 35.75 V^0.16 + 0.4275 T V^0.16 = 35.74 + 0.6215 × 20 − 35.75 × 1.5423 + 0.4275 × 20 × 1.5423 = 6.22 °F
- In metric: WCT = 13.12 + 0.6215 T − 11.37 V^0.16 + 0.3965 T V^0.16 gives -14.32 °C, the same value.
Wind chill chart
| Air temperature | 5 mph | 10 mph | 15 mph | 20 mph | 25 mph | 30 mph | 40 mph | 50 mph |
|---|---|---|---|---|---|---|---|---|
| 40 °F | 36 | 34 | 32 | 30 | 29 | 28 | 27 | 26 |
| 30 °F | 25 | 21 | 19 | 17 | 16 | 15 | 13 | 12 |
| 20 °F | 13 | 9 | 6 | 4 | 3 | 1 | -1 | -3 |
| 10 °F | 1 | -4 | -7 | -9 | -11 | -12 | -15 | -17 |
| 0 °F | -11 | -16 | -19 | -22 | -24 | -26 | -29 | -31 |
| -10 °F | -22 | -28 | -32 | -35 | -37 | -39 | -43 | -45 |
| -20 °F | -34 | -41 | -45 | -48 | -51 | -53 | -57 | -60 |
| -30 °F | -46 | -53 | -58 | -61 | -64 | -67 | -71 | -74 |
| -40 °F | -57 | -66 | -71 | -74 | -78 | -80 | -84 | -88 |
Each cell is the wind chill for that air temperature and wind speed, rounded to whole degrees.
How to Use the Wind Chill Calculator
- 1. Enter the air temperature and pick °F or °C. Use the actual air temperature, not an earlier wind chill figure.
- 2. Enter the wind speed and choose mph, km/h, m/s or knots. Use the speed measured at the usual 10 m (33 ft) anemometer height, which is what forecasts and weather stations report.
- 3. Read the wind chill and the risk level. The highlighted card is the feels-like value for exposed skin; the frostbite card gives the time exposed skin can take to freeze.
- 4. Check the working and the chart. The calculator shows the imperial and metric forms of the formula with your numbers, and a chart of neighbouring temperatures and wind speeds.
The 2001 Wind Chill Formula
Wind chill is how quickly bare skin loses heat in moving cold air, expressed as the calm-air temperature that would cool it as fast. The current formula was adopted in November 2001 by the United States and Canada (with the United Kingdom) after trials with human volunteers, replacing the Siple–Passel formula of the 1940s. In US units it is:
NWS wind chill temperature
WCT (°F) = 35.74 + 0.6215 T − 35.75 V^0.16 + 0.4275 T V^0.16
T is the air temperature in °F and V is the wind speed in mph.
Metric form: WCT (°C) = 13.12 + 0.6215 T − 11.37 V^0.16 + 0.3965 T V^0.16, with T in °C and V in km/h.
The model uses the wind at 5 ft, the height of an adult face, worked out from the standard 33 ft (10 m) anemometer reading. It assumes a person walking at about 4 mph, a face with typical skin resistance and a clear night with no sun. The NWS defines the index only for air temperatures of 50 °F (10 °C) or below and wind speeds above 3 mph; in lighter wind the air is treated as calm, and the calculator returns the air temperature. Environment Canada goes further and reports wind chill only when the temperature is 0 °C or colder and the wind is at least 5 km/h.
Worked example: 20 °F with a 15 mph wind
V^0.16 = 15^0.16 = 1.5423.
WCT = 35.74 + 0.6215 × 20 − 35.75 × 1.5423 + 0.4275 × 20 × 1.5423 = 6.2 °F (−14.3 °C).
It feels 13.8 °F colder than the air. In the metric form the same weather is −6.7 °C and 24 km/h, giving −14.3 °C.
Frostbite Risk Bands
Environment and Climate Change Canada publishes the risk levels below, by wind chill in °C. They are guidance for exposed skin, not a medical timer: wet skin, clothing, exertion, altitude and health all change the real risk, and in sustained winds over 50 km/h frostbite can come faster.
| Wind chill | Risk | Exposed skin can freeze in |
|---|---|---|
| 0 to −9 °C | Low | Not stated (slight discomfort) |
| −10 to −27 °C | Moderate | Not stated (risk after long exposure) |
| −28 to −39 °C | High | 10 to 30 minutes |
| −40 to −47 °C | Very high | 5 to 10 minutes |
| −48 to −54 °C | Severe | 2 to 5 minutes |
| −55 °C or colder | Extreme | Less than 2 minutes |
In US units, the first frostbite band begins at about −18 °F. The NWS chart marks exposed skin freezing in 30 minutes at a wind chill of −19 °F.
Worked example: −25 °C with a 40 km/h wind
WCT = 13.12 + 0.6215 × (−25) − 11.37 × 1.8044 + 0.3965 × (−25) × 1.8044 = −40.8 °C, where V^0.16 = 40^0.16 = 1.8044.
That is in the very high band: exposed skin can freeze in 5 to 10 minutes.
Frequently Asked Questions
- What is the wind chill formula?
- In US units, WCT = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, with T in °F and V in mph. The metric version is 13.12 + 0.6215T − 11.37V^0.16 + 0.3965TV^0.16, with T in °C and V in km/h. Both are the same equation written in different units.
- Is wind chill the real temperature?
- No. The air temperature does not change. Wind chill describes the rate at which exposed skin loses heat, so it applies to people and animals, not to objects like car engines or water pipes, which only cool down to the air temperature.
- At what temperature does wind chill apply?
- The NWS formula is valid at air temperatures of 50 °F (10 °C) or below and wind speeds above 3 mph. Canada reports it when the temperature is 0 °C or below. Above those temperatures the calculator does not give a wind chill.
- How long does it take to get frostbite?
- Canada's guidance is 10 to 30 minutes at a wind chill between −28 and −39 °C, 5 to 10 minutes between −40 and −47 °C, 2 to 5 minutes between −48 and −54 °C, and under 2 minutes at −55 °C or colder. Covered skin and good clothing greatly lengthen these times.
- Why was the wind chill formula changed in 2001?
- The older formula from the 1940s was based on how fast water froze in a container and overstated the cooling for people. The 2001 formula uses a model of the human face, heat transfer theory and trials with volunteers, and measures wind at face height instead of at the anemometer.
- Does wind chill matter if the wind is light?
- In winds at or below 3 mph the NWS treats the air as calm, so the wind chill equals the air temperature. Even a gentle breeze of 5 mph lowers the feels-like temperature of a 20 °F day by about 7 °F.